Page 24 - Pharmacognosy-I (02-06-06-102)

Structure of the Seed
A typical seed consists of
a - Embryo, which is developed from fertilized ovule.
b-The endosperm, which surrounds the embryo and developed from the
primary endosperm nucellus of the embryo sac.
c-The perisperm, which is formed from the nucellus.
d-All these structure (a,b and c) are protected by the testa, formed of one or
two seed-coats , which are originated from the integuments of the ovule

Testa:
The external features present on the surface of the testa are:
a-The hilum: which is the scar left on the seed where it separates from
the funicle or placenta.

b-The micropyle: which is minute opening in the seed coat which usually
marks the position of the radicle.

c-The Raphe: which is a ridge of fibrovascular tissue formed in seeds
derived from anatropous or amphitropous ovule by the adhesion of the
funicle and testa.

Outgrowth of Testa
The testa, during development of certain seeds, develop special out growths,
which are named differently according to their seat of origin; and their
nature, they may be:-

1- Arillus or Aril: it is membranous or fleshy expansion rises from
the funicle or hilar tissues and envelops the whole or part of the
seed as in Cardmom.

2- Arillode: it arises from the tissue of the micropyle and covers part
or whole of the seed e.g. Nutmeg.

3- Caruncle: is a localized fleshy or spongy out growth, formed from
the tissue in the neighborhood of the micropyle and covering it, as
in Ricinus.

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