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Purity

How to test for purity

PurityAnalysis

Author:  Deborah J. Lionakis Meyer

Date written: 22 April 2026

Purpose of a Purity Analysis

The purpose of a purity analysis is to determine and quantify the physical composition of a sample representing a seed lot.  The composition includes the species of seed under test and the contaminants, such as inert matter and seeds of other species.  The routine purity analysis typically includes the examination of a working sample weight approximately equal to 2500 seed units (ISTA 2026+; AOSA 2025+). Depending on the species under test, the weight of the working sample can be as little as one-one-hundredth of a gram (e.g., Juncus marginatus Rostk., grassleaf rush; Stromberg and Boudell 2013) up to a maximum of usually 1000 grams (e.g., Pinus edulis Engelm., pinyon pine; ISTA 2026+). The working sample is examined by trained specialists, the identity of the species under test is verified, and the components are separated and weighed. Results of the purity analysis are reported as percentages by weight for each component category; pure seed of the species under test, inert matter, and other species.  Additionally, a list of the types of inert matter and the names of any contaminating seeds found are provided.

Equipment used during the purity analysis can include magnifying lenses, microscopes, diaphanoscopes, sieves, seed blowers, forceps, and balances with appropriate weighing range accuracy for the size of sample under test.  Also important is access to a well vetted seed reference collection (seed herbarium) and a variety of seed identification references, either in print or online, used to make critical morphological identification of contaminating species and inert matter.

Seed Unit Versus Pure Seed

The composition of a seed unit may differ depending on the species being tested.  In general, a seed unit is described as “the structure usually regarded as a seed in planting practices and in commercial channels” (AOSA 2025+). A true seed (in the strict botanical sense – a ripened ovule) is the simplest type of seed unit; however, for many species, both cultivated and wild, the natural seed unit used for planting and in commerce is composed of more structures than just the true seed.

In the practice of seed testing, one further step is taken to identify what specific structures of a seed unit are to be included as part of the pure seed for a particular species. Detailed descriptions of pure seed representing several hundred agricultural, vegetable, herb, flower, turf, pasture, range, re-vegetation, tree, and shrub species are provided in the ISTA International Rules for Testing Seeds (ISTA 2026+) and the AOSA Rules for Seed Testing (AOSA 2025+). The ISTA Rules provide 63 types of pure seed definitions (PSD) and the AOSA Rules provide 51 pure seed unit (PSU) definitions, many of which are nearly the same for similar species included in both sets of seed testing procedures.  Any structure not mentioned in the PSD or PSU for a particular species is considered inert matter.  Additional information regarding the definitions of pure seed can be found in the ISTA Handbook on Pure Seed Definitions (ISTA 2010) and the AOSA Purity Testing Handbook (Meyer 2020).

True seeds may have structures, such as wings, arils, and hairs that are recognized as part of the pure seed (Figures 1 – 6).  Fruits, such as nutlets, schizocarps, mericarps, achenes, cypselae, pyrenes, samaras, etc., may also be recognized as pure seed. These fruits may have other floral parts (e.g., calyx, pappus, etc.) and accessory structures (e.g., bracts and stems) attached that may also be recognized as part of the pure seed (Figures 7 – 19).  In some cases, seed units may contain more than one seed or may contain no seed at all.  The latter situation usually occurs in species in which the fruit wall or other enclosing structures of the seed unit are thick or hardened.  In this case, it cannot be determined if a seed is present without dissection or x-ray examination (Figures 20 – 21). Such effort in the examination of 2500 seed units during the purity analysis is neither practical nor cost effective and could damage any potentially viable seeds.  Regardless of how many seeds are contained in a seed unit, it is treated as one pure seed for the purpose of purity analysis. With few exceptions, seed units that are immature, shriveled, broken. or insect damaged but are larger than one-half the original size, or those that have started to germinate, are also classified as pure seed.  For testing uniformity in practical application on seed lot quality evaluation, testing rules, such as ISTA (2026+) and AOSA (2025+) provide pure seed standards or definitions with balance and consensus.

For wild species that do not yet have standardized testing methods (ISTA or AOSA), it is recommended by the ISTA Wild Species Committee (WSC) that a pure seed definition assigned to a similar species in the testing rules be used.  For species included in the ISTA Wild Seeds Testing Protocols Database, we have provided pure seed definition numerical assignments that best match with definitions provided in the ISTA and the AOSA Rules. The purpose for suggesting pure seed definition assignments is to provide relatively comparable methods for physical quality evaluation of wild species lacking officially recognized testing methods.

Why is Pure Seed Important?

Similarity in how pure seeds are defined is critical for uniformity in purity analysis testing worldwide; this allows for comparison of test results within and among testing laboratories and for comparison of test results with seed lot labels in the marketplace or with contract requirements. Additionally, the pure seed from the purity analysis is usually used for germination testing, tetrazolium viability, seed counts, and a variety of other laboratory tests.  Seed units used for such tests must be taken indiscriminately from the pure seed regardless of maturity level, seed damage, or seed unit fill.  Each pure seed used for germination or tetrazolium viability testing is considered a single planting unit regardless of how many seeds it may contain.  Using a common pure seed definition for the species being tested provides a baseline for germination and tetrazolium tests, allowing for comparison of test results.  Ideally, for comparison of germination or tetrazolium viability tests to be valid all the other variables of these test methods need to align as well (e.g., test media, temperature, test duration, chemical solutions, evaluation criteria, etc.). 

Is Purity Analysis Important for Wild Seed?

Purity analysis can provide important information regarding planting value, such as how much seed is in a seed lot versus inert matter and the presence of seeds of other species (especially environmentally objectionable species).  For seeds of wild species that are easily cleaned of inert matter, results of a purity analysis can be useful to seed processing in determining if adequate cleaning has taken place without damaging the seed.  Conversely, for species with complex, chaffy, or fragile seed dispersal units, seed processing may be very difficult and may damage the seed units and their viability. In such cases, a purity analysis may be extremely difficult and time consuming to conduct and may only point out that the seed lot contains a large quantity of inert matter and very little seed, or that the inert matter cannot be easily separated from the pure seed (Figure 17). Testing of such species needs to be practical, cost effective, and reliably repeatable. The ISTA Rules provide a possible solution for just such a situation.  This is the testing of weighed replicates to determine the maximum germination potential of a seed lot.  In this test, four replicates that are of a weight containing approximately 100 seeds are planted and the number of normal seedlings emerging by the end of the test period is determined.  The result is reported as the number of normal seedlings in the total weight tested, the average weight of the four replicates, the average number of normal seedlings in four replicates, and the number of normal seedlings per kilogram.  The percentages by weight of a traditional purity analysis are not determined; however, the purity analysis working sample weight must be searched for seeds of all other species, which if found are identified and reported by number in the weight examined. Eucalyptus, Betula, and Chloris are examples of genera to which the ISTA Rules apply this method. 

Other Things to Consider

The most critical step in seed testing is sampling the seed lot.  This is particularly true for many wild species for which the seed may not be free-flowing and easy to properly sample with standard seed sampling equipment.  This step of the process is best left to trained and accredited seed samplers.  To the point, no matter how accurately a purity analysis is conducted, it can show only the quality of the sample submitted.  If the sample drawn is not representative of the seed lot, then neither is the purity analysis or any other tests conducted using that sample.

Once the seed lot sample is received by the testing laboratory, care must be taken to obtain the purity working sample from the submitted sample.  The ISTA (ISTA 2026+) and AOSA (AOSA 2025+) Rules provide specific methods for laboratory sampling that must be applied when obtaining the purity working sample. Visit the ISTA Bulking and Sampling Technical Committee webpage for instructional videos on laboratory seed sampling; ISTA Centrifugal Divider, ISTA Hand Halving, and ISTA Spoon Method (ISTA bulking sampling committee).

When the presence of weed seeds - especially objectionable or noxious weed species - is a concern, more extensive testing is recommended.  The ISTA and AOSA Rules provide methods for testing and reporting the numbers of seeds of such contaminants on a larger working sample (usually 10X the size of the purity analysis working weight) (ISTA 2026+; AOSA 2025+).  Results from this type of test can provide critical information on the potential environmental impact a wild species seed lot could have if contaminated with objectionable species. 

Conclusion

Whatever structures are included in the pure seed of a particular species, it is important to remember the need for consistency within and among laboratories so that purity analysis results can be compared. Additionally, whether a purity analysis is performed or not, the proper pure seed definition (PSD or PSU) must be used when selecting seeds for germination or tetrazolium viability tests; otherwise, the results of these tests cannot be compared among laboratories or with label claims.

References

Association of Official Seed Analyst (AOSA). 2025+.  AOSA Rules for Testing Seeds, Volume 1 Principles and Procedures. Association of Official Seed Analysts, Wichita, Kansas, USA.

International Seed Testing Association (ISTA). 2026+. International Rules for Seed Testing. The International Seed Testing Association, Wallisellen, Switzerland.

International Purity Committee.  2010.  ISTA Handbook on Pure Seed Definitions. 3rd Ed.  International Seed Testing Association, Bassersdorf, Switzerland.

Meyer, D. J. L. 2020. AOSA Purity Testing Handbook.  Contribution No. 41 – To the Handbook of Seed Testing.  Association of Official Seed Analysts, Washington, D.C., USA.

Stromberg, J. C. and Boudell, J. A.  2013. Floods, drought, and seed mass of riparian plant species. Journal of Arid Environments 97:99-107.

True seeds with wings, hairs, or arils

Figure 1.  Matthiola incana, Brassicaceae, true seed with peripheral wing.  The wing is part of the pure seed. ISTA PSD 11 and AOSA PSU 4.

Figure 2.  Pseudotsuga menziesii, Pinaceae, winged true seed, however only the portion of the wing immediately surrounding the seed is part of the pure seed. Under the ISTA Rules, seeds with the wing remaining attached are separated from those without a wing and the percentage by weight of each is determined; ISTA PSD 51.  Under the AOSA Rules, the portion of the wing extending beyond the seed is removed and classified as inert matter during the purity analysis; AOSA  PSU 5.

Figure 3.  Thuja plicata, Cupressaceae, winged true seed in which the entire wing is part of the pure seed; ISTA PSD 49 and AOSA PSU 4.

Figure 4.  Acacia decurrens, Fabaceae, true seed with aril concealing the hilum. The aril is part of the pure seed.  ISTA PSD 50 and the WSC recommends using AOSA PSU 7.

Figure 5.  Euphorbia cyparissias, Euphorbiaceae, true seed with attached aril (caruncle) concealing the hilum.  The aril (caruncle) is part of the pure seed. The WSC recommends using ISTA PSD 13 and AOSA PSU 6.

Figure 6.  Ipomoea pandurata, Convolvulaceae, true seed with hairy seed coat. The hairs are part of the pure seed. ISTA PSD 10 and AOSA PSU 1.

Fruits: Schizocarps and mericarps

Figure 7.  Trachyspermum ammi, Apiaceae, schizocarp (center) and mericarps (left and right) are pure seed. The attached pedicel (stem) is considered part of the pure seed.  The WSC recommends using ISTA PSD 15 and AOSA PSU 11 for this species.

Figure 8.  Malva parviflora, Malvaceae, schizocarp, mericarps, and seeds.  For this genus, mericarps and seeds are considered types of pure seed.  ISTA PSD 16 and the WSC recommends using AOSA PSU 30.

Fruits: Utricle and surrounding bracts (accessory structures)

Figure 9.  Krascheninnikovia lanata, Chenopodiaceae, seed enclosed in utricle (very thin, papery, semi-transparent pericarp) (right), surrounded by hair covered fruiting bracts (left). Both forms are pure seed.  AOSA PSU 38.

Fruits: Achenes with various attachments 

Figure 10a.  Layia platyglossa, Asteraceae, example of dimorphic achenes (different looking achenes produced by the ray and disk flowers). The term cypsela is a term also used for the fruit in Asteraceae due to the inferior position of the ovary in the flower, but the fruit is commonly called an achene in seed testing. In this image is a disk achene with pappus. The disk achene with attached pappus is classified as pure seed unless it can be determined no seed is present within the achene (AOSA PSU 50).

Figure 10b.  Layia platyglossa, Asteraceae, dorsal and ventral views of ray achenes enclosed in persistent bracts. A ray achene and its enclosing bract is classified as pure seed unless it can be determined no seed is present within the achene (AOSA PSU 50).

Figure 10c.  Layia platyglossa, Asteraceae, a ray achene removed from the bract. The ray achenes in this species are epappose (i.e., no pappus is formed). A ray achene without its enclosing bract is classified as pure seed unless it can be determined no seed is present within the achene (AOSA PSU 50).

Figure 11.  Carex hoodia, Cyperaceae, achene enclosed by the semi-transparent perigynium (a sac-like structure that surrounds the Carex flower).  The perigynium is part of the pure seed when present.  AOSA PSU 42 and the  WSC recommends using ISTA PSD 6.

Figure 12.  Rhynchospora macrostachya, Cyperaceae, achene with basally-attached bristles and apically-attached tubercle (enlarged style base).  The tubercle and bristles, if attached, are part of the pure seed.   The WSC recommends using ISTA 6 and AOSA 42.

Figure 13.  Geum coccineum, Rosaceae, achene with extended style (also referred to as beak, spine, or bristle – depending on the reference used).  The style is part of the pure seed if remaining attached. ISTA PSD 4 and AOSA PSU 39.

Fruits: Pods with attached calyx and bracts

Figure 14.  Kummerowia stipulacea, Fabaceae, true seeds (bottom row) and seed enclosed in one-seeded fruit with basally attached calyx and bracts (top row).  All structures may be part of the pure seed.  ISTA PSD 22 and AOSA PSU 9.

Fruits: Nutlets

Figure 15.  Nepeta racemosa, Lamiaceae, single seeded nutlets, each representing a lobe of the four-parted fruit in this family.  ISTA PSD 18 - The nutlet is pure seed unless it is obvious (by superficial examination only) no seed is present.  If upon such an examination of the nutlet it is obvious no seed is present, then it is classified as inert matter. AOSA PSU 10 - An intact nutlet is pure seed whether or not a seed is present; however, if the nutlet is broken and no seed is present, then it is inert matter.

Fruits: Pyrenes

Figure 16  Prunus fasciculata, Rosaceae, pyrenes (seed enclosed in hardened endocarp; also called a stone or kernel) removed from the fleshy portion of the single seeded fruit (drupe).  ISTA PSD 56 - The pyrene is pure seed unless it is obvious (by superficial examination only) no seed is present.  If upon such an examination of the pyrene it is obvious no seed is present, then it is classified as inert matter. AOSA PSU 34 - An intact pyrene is pure seed whether or not a seed is present; however, if the pyrene is broken and no seed is present, then it is inert matter.  For both ISTA and AOSA the seed with the endocarp partially or entirely removed is pure seed.

Fruits: Samaras

Figure 17a.  Betula pendula, Betulaceae, bi-winged fruit (samara) with two attached styles containing one seed (circled in red), the remaining structures in the image are fruiting bracts (no seeds present).  In this image, only the bi-winged samara is pure seed, everything else is inert matter; ISTA PSD 53 and AOSA PSU 26.  

Figure 17b.  Betula pendula, Betulaceae.  Bi-winged samara of Betula pendula. Due to the difficulty of separating the fruiting bracts from the fragile winged fruits ISTA recommends testing members of this genus using the weighed replicate method rather than a traditional purity analysis.

Figure 18.  Casuarina equisetifolia, Casuarinaceae, winged fruit (samara) containing one seed; AOSA PSU 26 and recommend using ISTA PSD 53.

Seed units with attached stems

Figure 19.  Andropogon hallii, Poaceae, single caryopsis spikelet with attached rachis and pedicel segments (stem segments).  Sometimes there will be a sterile spikelet attached to the pedicel.  All structures shown here may be part of the pure seed: ISTA  PSD 42 and AOSA PSU 16.

Seed units containing more than one seed

Figure 20a.  Bouteloua dactyloides, Poaceae, bur that may contain more than one spikelet, each with or without a caryopsis (all parts shown here are part of a pure seed). Because of the hardened outer structures of the bur, it is not necessary to check if a caryopsis is present in the bur; the bur is considered pure seed.  Free caryopses are pure seed.  ISTA PSD 42 and AOSA PSU 19.

Figure 20b. Bouteloua dactyloides, Poaceae, transverse section of bur showing multiple spikelets; in this case, two with caryopses and three without caryopses (image by D. Meyer).

Figure 20c. Bouteloua dactyloides, Poaceae,  x-ray showing empty and caryopsis filled burrs (image by D. Meyer).

Figure 21a.  Sanguisorba minor, Rosaceae, two achenes are usually enclosed in a hypanthium (dry persistent floral tube).  ISTA PSD 3 - The achene with or without hypanthium is pure seed unless it is obvious (by superficial examination only) no seed is present.  If upon such an examination of hypanthium or achene it is obvious no seed is present, then it is classified as inert matter. AOSA PSU 34 - An intact achene, with or without hypanthium is pure seed whether or not a seed is present; however, if the hypanthium or achene is broken and no seed is present, then it is inert matter.  For both ISTA and AOSA the seed with hypanthium and achene wall (pericarp) removed is pure seed.

Figure 21b. Sanguisorba minor, Rosaceae, longitudinal section of hypanthium revealing two achenes, each containing a single seed (Image by D. Meyer).

Methodology

purity analysis

  • Purity analysis. The objective of a purity analysis is to determine the physical composition of the working sample. The analysis shall include the identification of the kind, or kind and cultivar of seed under consideration, and all contaminating species and inert matter. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

  • Purity. The term “purity” means the name or names of the kind, type, or variety and the percentage or percentages thereof; the percentage of other agricultural seed or crop seed; the percentage of weed seeds, including noxious-weeds seeds; the percentage of inert matter; and the names of the noxious-weed seeds and the rate of occurrence of each. Agricultural Marketing Service, USDA. Federal Seed Act, Part 201. Federal Seed Act Regulations. 201.2 Terms Defined. Current as of May 21, 2020.

seed lot

  • Seed lot. A seed lot is a specified quantity of seed that is physically and uniquely identified. 2020 International Rules for Seed Testing, (ISTA)

  • Lot of seed. The  term "lot of seed" means a definite quantity of seed identified by a number, every portion or bag which is uniform, within permitted tolerances, for the factors which appear in the labeling. Agricultural Marketing Service, USDA. Federal Seed Act, Part 201. Federal Seed Act Regulations. 201.2 Terms Defined. Current as of May 21, 2020.

species

  • Species. A category of classification lower than a genus that is made up of plants which possess in common distinctive characteristics that are reproduced in their offspring. The species name included second to the genus in the scientific binomial. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

seed, seeds

  • Seed. The part of a plant which is able to develop into a new plant. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Seed. Botanically, a seed is a mature fertilized ovule containing an embryonic plant; usually it has nutrient storage tissue and is surrounded by a protective coat, the testa. This structure is a "true seed"; however, the ovules of many species have additional structures of the mother plant attached or fused to the seed coat. For example, the "seed" of Triticum aestivum (wheat) is botanically a fruit because the pericarp (ovary wall) is fused with the seed coat. In these rules the term "seed" will be used in the agronomic sense (i.e. the true seed plus any accessory structures that may be attached when it is planted in the field; see section 3.2 of the AOSA Rules for Testing Seeds Vol. 1). Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 4, 2019

  • Seed. The ripened ovule, enclosing the rudimentary plant and food necessary for its germination. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

inert matter

  • Inert matter.  Inert matter shall include seeds and seed-like structures from both crop and weed plants and other materials not described in section 3.2 and Table 3A or can be described as follows: seeds and seed-like structure from crop and weed plants and other non-seed matter. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

seed, seeds

  • Seed. The part of a plant which is able to develop into a new plant. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Seed. Botanically, a seed is a mature fertilized ovule containing an embryonic plant; usually it has nutrient storage tissue and is surrounded by a protective coat, the testa. This structure is a "true seed"; however, the ovules of many species have additional structures of the mother plant attached or fused to the seed coat. For example, the "seed" of Triticum aestivum (wheat) is botanically a fruit because the pericarp (ovary wall) is fused with the seed coat. In these rules the term "seed" will be used in the agronomic sense (i.e. the true seed plus any accessory structures that may be attached when it is planted in the field; see section 3.2 of the AOSA Rules for Testing Seeds Vol. 1). Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 4, 2019

  • Seed. The ripened ovule, enclosing the rudimentary plant and food necessary for its germination. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

ISTA

International Rules for Seed Testing

AOSA

International Rules for Seed Testing

inert matter, inert

  • Inert matter.  Inert matter shall include seeds and seed-like structures from both crop and weed plants and other materials not described in section 3.2 and Table 3A or can be described as follows: seeds and seed-like structure from crop and weed plants and other non-seed matter. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

seed herbarium

  • Seed herbarium. A reference collection of validated and preserved seeds, fruits and other propagules used for scientific study or seed identification. TWS

variety

  • Variety. A group of plants related by descent but distinguished from other similar groups by characters too trivial to entitle it to recognition as a species. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

seed unit

  • Seed unit. Commonly found dispersal unit, i.e. achenes and similar fruits, schizocarps, florets etc., as defined for each genus or species in the ISTA Rules, Table 3B Parts 1 & 2. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Seed unit. The structure usually regarded as a seed in planting practices and in commercial channels. Refer to section 3.2 e for pure seed unit definitions. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

  • Seed Unit. Commonly found dispersal unit, i.e. achenes and similar fruits, schizocarps, florets etc, as defined for each genus or species in the Pure Seed Definitions in Table 3B parts 1 and 2. 2020 International Rules for Seed Testing (ISTA)

true seed, true seeds

  • True seed. A mature fertilized ovule consisting of an embryo, with or without an external food reserve (e.g. endosperm) enclosed by the testa. SCST Seed Technologist Training Manual, 2018
 

ovule

  • Ovule. The immature seed within the ovary. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Ovule. A structure, consisting of a female gametophyte, nucellus, and integuments, which develops into a seed after fertilization. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

pure seed unit

  • Pure seed unit (PSU). The seed units described in Table 3A shall be considered pure seed. Structures not specifically described as part of the PSU shall be removed and classified as inert matter (refer to section 3.5). Seeds of other species adhering to seed units of the kind under consideration shall be detached and classified as either weed seed or other crop seed (refer to section 4). The PSU numbers given for species in Table 2A correspond to the PSU numbers in Table 3A. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

pure seed unit, psu

  • Pure seed unit (PSU). The seed units described in Table 3A shall be considered pure seed. Structures not specifically described as part of the PSU shall be removed and classified as inert matter (refer to section 3.5). Seeds of other species adhering to seed units of the kind under consideration shall be detached and classified as either weed seed or other crop seed (refer to section 4). The PSU numbers given for species in Table 2A correspond to the PSU numbers in Table 3A. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

true seed, true seeds

  • True seed. A mature fertilized ovule consisting of an embryo, with or without an external food reserve (e.g. endosperm) enclosed by the testa. SCST Seed Technologist Training Manual, 2018
 

wing, wings

  • Wing. A flat membranous outgrowth from a fruit or seed. 2020 International Rules for Seed Testing (ISTA)

  • Wing. A flat membranous outgrowth from a fruit or seed (e.g. Coreopsis, Dimorphotheca). ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Wing. Lateral petal of a papilionaceous corolla, as in some legumes. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

hair, hairs

  • Hair. A uni- or multicellular outgrowth of the epidermis. 2020 International Rules for Seed Testing (ISTA)

  • Hair. An elongated uni- or multicellular outgrowth of the epidermis (e.g. in Anemone). ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

nutlet, nutlets

  • Nutlet. A small nut. 2020 International Rules for Seed Testing (ISTA)

  • Nutlet. A small nut, a one seeded portion of a fruit originating from half of a carpel (e.g. Boraginaceae, Lamiaceae and Verbinaceae). ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Nutlet. A dry, one-seeded, indehiscent section of a fruit in the Boraginaceae, Lamiaceae and Verbenaceae. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

calyx

  • Calyx, calyces (plural). The outer floral envelope composed of the sepals. 2020 International Rules for Seed Testing (ISTA)

  • Calyx, calyces (plural). The outer floral envelope of dicotyledons, composed of the sepals. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010.

  • Calyx. The outer cycle of the perianth; the sepals considered collectively. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

pappus

  • Pappus. A ring of fine, sometimes feathery hairs or scales, crowning an achene. 2020 International Rules for Seed Testing (ISTA)

  • Pappus. A ring of fine, sometimes feathery hairs or scales, crowning an achene in Asteraceae. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Pappus. The teeth, awns, etc., surmounting the achene of the Asteraceae family. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

accessory structures

  • Accessory structures. In seed testing: structures other than the seed and fruit. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

fruit

  • Fruit. The structure that develops from the pericarp as the enclosed seed or seeds mature. Fruits may have the following attributes: Succulent or dry, depending on whether or not the middle layer of the pericarp (mesocarp) develops into a fleshy covering; Dehiscent or indehiscent, according to whether or not the fruit wall splits open to release the seed; True or simple fruits, which develop from the gynoecium of a single flower, and multiple fruits, which develop from a complete inflorescence; Monocarpellary or polycarpellary, depending on whether they developed from a single ovary or from a number of fused ovaries. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Fruit. In angiosperms, a mature ripened ovary, usually containing seeds. Some authors include extracarpellary parts adhering to the ovary at maturity. SCST Seed Technologist Training Manual, 2018

  • Fruit. The ripened ovary of a seed plant and associated parts. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

x-ray, x-rays

x-ray. An image taken with x-rays. TWS

viable

  • Viable. Alive. Seed viability indicates that a seed contains structures and substances including enzyme systems that give it the capacity to germinate under favorable conditions in the absence of dormancy.  SCST Seed Technologist Training Manual, 2018 

germination

  • Germination. Germination of a seed in an ISTA test is the emergence and development of the seedling to a stage where the aspect of its essential structures indicates whether or not it is able to develop further into a satisfactory plant under favourable conditions in the field. 2020 International Rules for Seed Testing, (ISTA)

  • Germination (seed testing definition).The emergence and development from the seed embryo of those essential structures which, for the kind of seed in question, are indicative of its ability to produce a normal plant under favorable conditions. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

  • Germination (physiological definition). A process involving water uptake, metabolic changes and cell elongation resulting in radicle emergence from the seed. SCST Seed Technologist Training Manual, 2018

viable, viability

  • Viable. Alive. Seed viability indicates that a seed contains structures and substances including enzyme systems that give it the capacity to germinate under favorable conditions in the absence of dormancy.  SCST Seed Technologist Training Manual, 2018 

normal seedling, normal

  • Normal seedling. A seedling with all essential structures present and capable of developing into a plant under favorable conditions; certain defects may be present if they are judged to be not so severe as to impede further development of the plant (see abnormal seedling). Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 4, 2019

seedling, seedlings

  • Seedling. A young plant developing from the embryo of a seed. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 4, 2019

standard

  • Standard. The large upper petal of a papilionaceous corolla, as in some legumes. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

purity working sample

  • Purity working sample. The sub-sample taken from the submitted sample on which the purity analysis is performed. See sections 2.3 b and 3.  Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

centrifugal divider, Gamet divider

  • Centrifugal divider.  Gamet type, the divider makes use of centrifugal force to mix and scatter seeds over the dividing surface. The seed flows downward through a hopper onto a shallow rubber cup or spinner. Upon rotation of the spinner by an electric motor the seeds are thrown out by centrifugal force and fall downward. The circle or area where the seeds fall is equally divided into two parts by a stationary baffle so that approximately half the seeds fall in one spout and half in the other spout. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

wing, wings

  • Wing. A flat membranous outgrowth from a fruit or seed. 2020 International Rules for Seed Testing (ISTA)

  • Wing. A flat membranous outgrowth from a fruit or seed (e.g. Coreopsis, Dimorphotheca). ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Wing. Lateral petal of a papilionaceous corolla, as in some legumes. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

entire

  • Entire. Without divisions, lobes, or teeth; usually refers to margins of leaves, petals, and sepals. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

aril, arillus

  • Aril, arillus, arilli (plural). a fleshy, often coloured covering or appendage of some seeds; an outgrowth of the funicle or base of the ovule (caruncle, strophiole). ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010.
     
  • Aril. A fleshy outgrowth of the ovule or funiculus. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

hilum

  • Hilum. Scar on a seed coat marking the place of attachment of the seed stalk to the seed. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111
 

caruncle, caruncles

  • Caruncle. A small outgrowth of the micropyle (e.g. Ricinus) (aril, strophiole). ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010.

  • Caruncle. A hardened aril. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

hairy

  • Hairy. Bearing hairs. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

schizocarp

  • Schizocarp. A dry fruit which separates into two or more units (mericarps) at maturity. 2020 International Rules for Seed Testing (ISTA)

  • Schizocarp. A dry fruit which separates into two or more single seeded units (mericarps) at maturity, e.g. in Apiaceae. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Schizocarp. A dry fruit that splits into one-seeded segments (mericarps) at maturity. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

pedicel

  • Pedicel. The stalk of each single flower in an inflorescence. 2020 International Rules for Seed Testing (ISTA)

  • Pedicel. A small stalk, the stalk of a single flower in an inflorescence. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Pedicel. The stalk of a floret in an inflorescence or of a grass spikelet. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

  • Pedicel. The stalk of an individual flower or spikelet of an inflorescence. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

genus

  • Genus. A group of closely related species. The genus name is the first word of a binomial scientific name and is capitalized. The plural form of the word is genera. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

utricle

  • Utricle. A dry, thin-walled, one-seeded, bladder-like fruit. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

pericarp, pericarps

  • Pericarp [fruit coat]. The wall of the mature ovary or fruit. 2020 International Rules for Seed Testing (ISTA)

  • Pericarp. The ovary wall. the fruit coat enclosing the seed. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Pericarp. Fruit wall. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

  • Pericarp. The wall of a ripened ovary; the fruit coat.  Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

hair, hairs

  • Hair. A uni- or multicellular outgrowth of the epidermis. 2020 International Rules for Seed Testing (ISTA)

  • Hair. An elongated uni- or multicellular outgrowth of the epidermis (e.g. in Anemone). ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

fruiting bract, fruiting bracts

  • Fruiting bract. A small or rudimentary leaf or leaf-like structure near the base of a fruit that may or may not enclose the fruit. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

dimorphic

  • Dimorphic. An object having two forms. SCST Seed Technologist Training Manual, 2018

ray

  • Ray. Corolla of a marginal flower of a composite inflorescence. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

cypsela

  • Cypsela. A fruit similar to an achene except that it develops from an inferior ovary, and thus also includes non-carpellary tissue. It is typical of the Asteraceae, in which the fruit is surrounded by hairs derived from the calyx. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010.
 

ovary

  • Ovary. The basal, expanded part of the pistil that contains the ovules. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Ovary. The basal enlarged portion of a pistil within which seeds develop. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

achene, achenium

  • Achene, achenium. A dry, indehiscent, one-seeded fruit, formed from one free carpel (e.g. Ranunculaceae, Geum) with the seed coat distinct from the fruit coat; occasionally consisting of more than one carpel (Asteraceae). 2020 International Rules for Seed Testing (ISTA)

  • Achene, achenium. A dry, indehiscent, one-seeded fruit, formed strictly from one free carpel, and with the testa distinct from the fruit wall, e.g. Ranunculaceae, Geum, occasionally consisting of more that one carpel, e.g. Asteraceae. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010.

  • Achene. A dry, one-chambered, one-seeded indehiscent fruit with the seed attached to the fruit wall at a single point. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

  • Achene. A one-celled, dry indehiscent fruit in which the testa and pericarp are not firmly attached. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

dorsal

  • Dorsal. The side facing away from the axis; the upper part. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010.

  • Dorsal. Relating to the back of a structure of organ. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

  • Dorsal. In general 'dorsal' refers to the rear or ack or upper surface. TWS

ventral

  • Ventral. The side facing towards the axis; the lower surface (dorsal). ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Ventral. The lower or front side; opposite to dorsal. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

persistent

  • Persistent. Remaining attached after other parts have been shed. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

bract

  • Bract. A reduced leaf or scale-like structure subtending a flower or a grass spikelet in its axil. 2020 International Rules for Seed Testing, (ISTA)

  • Bract. In angiosperms: A small or rudimentary leaf or leaf-like structure near the base of a flower or inflorescence. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

  • Bract. A modified leaf associated with a flower or inflorescence. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

bristle, bristles

  • Bristle. A stiff hair; sometimes applied to the upper part of an awn, when the latter is bent. 2020 International Rules for Seed Testing (ISTA)

  • Bristle. A stiff hair, the upped part of an bent awn. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010.

  • Bristle. A short stiff hair. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

style

  • Style. The slender stalk that bears the stigma. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Style. The slender part of the pistil supporting the stigma. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

beak, beaks

  • Beak [-ed]. A long, pointed prolongation of a fruit. 2020 International Rules for Seed Testing (ISTA)

  • Beak. A long, pointed prolongation of a fruit (e.g. Anemone, Geranium, Geum). ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010.

  • Beak. A point or projection, as on the glume of a wheat spikelet. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

bristle, bristles

  • Bristle. A stiff hair; sometimes applied to the upper part of an awn, when the latter is bent. 2020 International Rules for Seed Testing (ISTA)

  • Bristle. A stiff hair, the upped part of an bent awn. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010.

  • Bristle. A short stiff hair. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

lobe

  • Lobe. A segment of an organ, usually rounded or obtuse. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

nutlet, nutlets

  • Nutlet. A small nut. 2020 International Rules for Seed Testing (ISTA)

  • Nutlet. A small nut, a one seeded portion of a fruit originating from half of a carpel (e.g. Boraginaceae, Lamiaceae and Verbinaceae). ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Nutlet. A dry, one-seeded, indehiscent section of a fruit in the Boraginaceae, Lamiaceae and Verbenaceae. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

endocarp

  • Endocarp. The inner layer of the pericarp. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Endocarp.  The innermost layer(s) of the pericarp (fruit wall). SCST Seed Technologist Training Manual, 2018

stone

  • Stone. In a drupe, the hardened endocarp containing a kernel. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

kernel

  • Kernel. A seed within a stone. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Kernel. A whole grain or caryopsis of a cereal. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

drupe, drupes

  • Drupe. Indehiscent, one-seeded fruit with stony endocarp and fleshy outer layers. 2020 International Rules for Seed Testing (ISTA)

  • Drupe. A fleshy indehiscent fruit in which the seed or seeds are surrounded by a hardened en-docarp, as in Prunus avium. The endocarp may replace the testa in its protective role, and may also play part in the dormancy mechanism. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Drupe. An indehiscent fruit with a fleshy outer layer and a stony inner layer surrounding the seed. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

pyrene

  • Pyrene. Seed enclosed by the hard endocarp from a drupe (or similar structures from multi-seeded fruits). 2020 International Rules for Seed Testing (ISTA)

  • Pyrene, A seed enclosed by the hard endocarp of a drupe, or similar structures from multi-seeded fruits, also kernel or stone (see drupe for illustrations). ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Pyrene. The hard, indehiscent, one-seeded portion of a drupe or drupelet (stone or pit). Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

samara

  • Samara. An indehiscent, winged fruit; a type of achene with a pericarp extended into a membranous wing to aid wind dispersal of the seed, e.g. the winged fruits or keys of Fraxinus excelsior. The double samara typical of Acer is a kind of schizocarp. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Samara. A dry, indehiscent fruit, with a wing-like extension of the pericarp. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

caryopsis

  • Caryopsis. In grasses: A dry, one-seeded, indehiscent fruit with the pericarp fused to the seed coat (testa). Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

  • Caryopsis. Naked grass-fruit in which the testa is united with the pericarp. 2020 International Rules for Seed Testing (ISTA)

  • Caryopsis. A naked grass fruit in which the testa is fused with the pericarp; also a grain. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010.

  • Caryopsis. The fruit of a grass, which is dry, one-seeded, indehiscent, with the testa and the pericarp completely united. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

spikelet, spikelets

  • Spikelet. The unit of a grass inflorescence comprising one or more florets subtended by one or two sterile glumes. For the purposes of the Rules, the term spikelet includes, as well as a fertile floret, either one or more additional fertile or completely infertile florets, or glumes. 2020 International Rules for Seed Testing (ISTA)

  • Spikelet. Part of a grass inflorescence including one or more florets subtended by one or two glumes. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Spikelet. In grasses: One or more attached florets usually subtended by one or more bracts (glumes). Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

  • Spikelet. The unit of a grass inflorescence that consists of a pair of empty glumes that enclose one of more florets arranged around a rachilla. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

rachis, rhachis

  • Rachis, rhachis, rachides (plural). The main axis of an inflorescence. 2020 International Rules for Seed Testing (ISTA)

  • Rachis. The main axis of an inflorescence (or compound leaf). Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

  • Rachis. The axis of a spike or raceme. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

sterile

  • Sterile. Without functional sex organs (for grass florets: without caryopsis). 2020 International Rules for Seed Testing (ISTA)

  • Sterile. Without pistils. A sterile floret may be staminate or neuter. It may even lack a palea, and consist of nothing but a lemma. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

caryopsis, caryopses

  • Caryopsis. In grasses: A dry, one-seeded, indehiscent fruit with the pericarp fused to the seed coat (testa). Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

  • Caryopsis. Naked grass-fruit in which the testa is united with the pericarp. 2020 International Rules for Seed Testing (ISTA)

  • Caryopsis. A naked grass fruit in which the testa is fused with the pericarp; also a grain. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010.

  • Caryopsis. The fruit of a grass, which is dry, one-seeded, indehiscent, with the testa and the pericarp completely united. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

spikelet, spikelets

  • Spikelet. The unit of a grass inflorescence comprising one or more florets subtended by one or two sterile glumes. For the purposes of the Rules, the term spikelet includes, as well as a fertile floret, either one or more additional fertile or completely infertile florets, or glumes. 2020 International Rules for Seed Testing (ISTA)

  • Spikelet. Part of a grass inflorescence including one or more florets subtended by one or two glumes. ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010

  • Spikelet. In grasses: One or more attached florets usually subtended by one or more bracts (glumes). Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

  • Spikelet. The unit of a grass inflorescence that consists of a pair of empty glumes that enclose one of more florets arranged around a rachilla. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111

hypanthium

  • Hypanthium, hypanthia (plural). A ring-like, cup-like or tubular structure which surrounds the ovary and on which sepals, petals and stamens are borne. 2020 International Rules for Seed Testing (ISTA)

  • Hypanthium. A cup-shaped structure surrounding the ovary, derived either from the fusion of floral parts or an extension of the receptacle to which the floral parts are attached. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 1, 2019

longitudinal

  • Longitudinal. Running lengthwise rather that across. TWS