Seed Morphology

General Information on Seed and Fruit

Data and images presented here were captured by the Millennium Seed Bank's Seed Morphologist Wolfgang Stuppy assisted by Gemma Hoyle, Elly Vaes and Hanny Morales.

Fruit size

(l × w × t) The size of the fruit is measured in length (l) × width (w) × thickness (t). Length refers to the dimension from the point of attachment to the tip of the fruit (or the opposite end). Width and thickness are two lateral dimensions which may or may not be identical, e.g. in a compressed fruit the larger lateral diameter would be referred to as width and the smaller one as thickness.

Fruit type:

Fruit type is based on Spjut 1994.

caryopsis with lemma and palea attached
caryopsis without lemma and palea attached
compound cone
dry dehiscent multiple fruit
dry indehiscent multiple fruit
fleshy dehiscent multiple fruit
loculicidal capsule
poricidal capsule
septicidal capsule
simple cone


This refers to the actual dispersal unit. If a fruit is dehiscent, the dispersal unit or diapsore is usually the seed. Indehiscent fruits do not open to release their seeds. In these cases, the seeds are distributed together with the entire fruit (the pericarp or other floral parts, e.g. the calyx) or part of the fruit (e.g. the schizocarpic but indehiscent sarmarium of Acer or the segments of a lomentum of some legumes). The following options are used: seed, entire fruit, partial fruit, segment of lomentum or entire plant.

Mechanical protection of the seed:

Indehiscent fruits release their seeds to the environment. Seeds from dehiscent fruits usually develop hardened seed coats that provide the mechanical protection of the seed. In indehiscent fruits other than berries, it is the entire fruit wall (pericarp, e.g. in nuts) or part of it (usually the inner layer, called endocarp, e.g. in drupes) that provides the mechanical protection of the seed. The mechanical protection can also be provided by a hard endosperm (e.g. grasses, palms, Guaiacum). In grasses the lemma and/or palea can remain attached to the grain and provide mechanical protection and the lemma, palea and endosperm have been observed together. Rarely (only in Cactaceae-Opuntioideae) a woody funiculus wraps around the seeds. The options are: seed coat, pericarp, endocarp, calyx, perianth, bracts or bracteoles, lemma and palea, lemma, palea and endosperm or funiculus.

The seed

Seed size (l × w × h): The measurements of the seed are given as length (l) × width (w) × height (h). Length refers to the distance between the chalazal and micropylar end of the seed, width is the lateral diameter (the distance between the flanks of the seed) and height (thickness) is the distance between the ventral (raphal) side and the dorsal side. If the seeds are campylotropous and only have short or no raphe, the longest diameter that runs parallel to the axes connecting the chalaza and micropyle is taken as the length.

The diaspore

Diaspore size (l × w × t): The size of the diaspore is measured in length (l) × width (w) × thickness (t). Length refers to the dimension from the point of attachment to the plant to the tip of the diaspore (or the opposite end), width and thickness are two lateral dimensions which may or may not be identical, e.g. in a compressed diaspore the larger lateral diameter is referred to as width and the smaller one as thickness.

Dispersal aids:

Refers to anything assisting the diaspore to travel away from the mother plant e.g., wings, hairs or a foveolate surface for wind dispersal, fleshy parts to attract animals or hooks to attach to them. The options are: none, hairs, hooks, wing or foveolate surface.

Internal Seed Morphology

Seed configuration:

It is observed whether the longitudinal axis of the seed is straight or bent. All seeds with a bent longitudinal axis (and then usually also with bent embryos) are called campylotropous. If the seed has a straight axis it is usually anatropous, sometimes hemianatropous. The options used are: anatropous, orthotropous (= atropous), hemitropous (= hemianatropous), campylotropous, ana-campylotropous, ortho-campylotropous, hemi-campylotropous (= hemiana-campylotropous) or obcampylotropous.

Type of Embryo:

The type of embryo is based in accordance to Martin's (1946) classification. Martin's twelve different embryo types are: basal-broad, basal-capitate, basal-lateral, peripheral, axial-linear, axial-dwarf, axial-micro, axial-spatulate, axial-investing, axial-bent, axial-folded or rudimentary.

Relative size of embryo:

With respect to the relative size of the embryo (and reciprocally the endosperm), Martin (1946) suggested a quantitative classification system instead of applying rather vague terms accepting that a small embryo implies copious endosperm and copious endosperm implies a small embryo. Martin's quantitative system consists of five size-designations representing approximately quarter-unit volumetric proportions of embryo to endosperm: small (¼ minus), quarter (¼ plus), half (½ plus), dominant (¾ plus), and total. The relative size of the embryo is estimated by examining both a longitudinal and a cross section of a seed.

Image Filenames

They follow the principle: "Genus_species_#_S_CS", whereby # is the sequential number for images taken for a certain taxon, the letter(s) following the number stand for:

  • "diaspore" (D) or "diaspores" (DD)
  • "fruit" (F) or "fruits" (FF)
  • "infructescence" (IN)
  • "mericarps" (MC)
  • "parent plant" (PP)
  • "seed" (S) or "seeds" (SS)
  • "seed and fruit" (SF)
  • "seeds and fruits" (SSFF)

The last two letters stand for:

  • "anatomical cross section" (AC)
  • "anatomical longitudinal section" (AL)
  • "apical view" (AV)
  • "basal view" (BV)
  • "cross section" (CS)
  • "dorsal view" (DV)
  • "embryo" (EM)
  • "germinating seed" (GE)
  • "longitudinal section" (LS)
  • "lateral view" (LV)
  • "various orientations" (only in combination with SS or FF) (VO)
  • "ventral view" (VV)
  • "illustration" (IL)

Key References for Morphology Module in SID

  • Boesewinkel, F.D. and Bouman, F. 1984: The seed: structure. In: Embryology of angiosperms (ed. B.M.Johri), pp. 567-610. Springer Verlag, Heidelberg.
  • Boesewinkel, F.D. and Bouman, F. 1995: The seed: structure and function. In: Seed Development and germination (eds J. Kigel & G. Galili), pp. 1-24. Marcel Dekker, New York.
  • Bouman, F. 1984: The ovule. In: Johri, J.B. (ed.): Embryology of the angiosperms, pp. 123-157. Springer Verlag, Berlin, Heidelberg, New York, Tokyo.
  • Bouman, F. & Boesewinkel, F.D. 1991: The campylotropous ovules and seeds, their structure and functions. Bot. Jahrb. Syst. 113(2/3): 255-270.
  • Corner, E.J.H. 1976: The seeds of dicotyledons. Cambridge University Press, Cambridge.
  • Cronquist, A. 1988: The evolution and classification of flowering plants. 2nd ed. The New York Botanical Garden, Bronx.
  • Esau, K. 1965: Plant anatomy, 2nd ed. John Wiley & Sons, Inc., New York, London, Sydney.
  • Fahn, A. 1990: Plant anatomy, 4th ed. Pergamon Press, Oxford.
  • Gunn, C.R. 1981: Seeds of the Leguminosae. — In: Polhill, R.M. & Raven, P.H. (eds.), Advances in Legume Systematics. — Int. Legume Conf. K, Proc. 1978, V. 2. Min. Agr., Fisheries and Food, Richmond, England, pt. 2, pp. 913-925.
  • Gunn, C.R. 1984: Fruits and seeds of genera in the subfamily Mimosoideae (Fabaceae). - U.S.D.A. Agric. Res. Serv. Techn. Bull. 1681: 1-194.
  • Gunn, C.R. 1991: Fruits and seeds of genera in the subfamily Caesalpinioideae (Fabaceae). U.S.D.A. Agric. Res. Serv. Techn. Bull. 1755: 1-408.
  • Johri, B.M., Ambegoakar, K.B. & Srivastava, P.S. 1992: Comparative embryology of angiosperms. Vol 1 + 2. Springer Verlag, Berlin, Heidelberg, New York, Tokyo.
  • Kapil, R.N., Bor, J. & Bouman, F. 1980: Seed appendages in angiosperms. I. Introduction. Bot. Jahrb. Syst. 101(4): 555-573.
  • Martin, A.C. 1946: The Comparative Internal Morphology of Seeds. American Midland Naturalist 36, 513-660
  • Roth, I. 1977: Fruits of angiosperms. Gebrüder Bornträger, Berlin & Stuttgart. 675 pp.
  • Spjut, R.W. 1994: A systematic treatment of fruit types. Mem. New York Bot. Gard. 70:1-182.
  • Vaughan, J.G. 1970: The structure and utilisation of oil seeds. Chapman & Hall, London, UK.
  • Werker, E. 1997: Seed anatomy. Gebrüder Bornträger, Berlin, Stuttgart (Encyclopedia of plant anatomy, Vol. 10, Part 3.)