The seed Definition: The Seed is a mature fertilized ovule containing an embryo (originated from fertilized ovules). The function of the seed is to ensure the propagation of the plant.

Structure of Mature ovulestigma style micropyle Ovary wall Ovum (zygot) Outer integument

nucellus

Polar nuclei

1ry endosperm nucellus

Embryo sac [ 7-8 nuclei ] Inner integument Antipodal cells chalaza funicle

Vascular bundle

Outgrowths of testa 1- Arillus or Arili It arises from the funicle or from the tissue of the hilum and partly or completely enveloping the seed. It may be fleshy as in texture or dry and membranous as in Cardamom. 2- Arillode It arises from the tissue of the micropyle and partly or completely covering the seed, being usually fleshy as in Euonymus. N.B. The outgrowth of Nutmeg, named mace, arises from the tissues of both funicle and micropyle and thus it is considered as Arillus or Arillode. 3- Caruncle It is a localised fleshy outgrowth, formed from the tissue in the neighbourhood of the micropyle and covers it as in Ricinus and Croton seeds. 4- Strophiole It is a local, usually barrel-shaped enlargement along the line of the raph, due to an increase in the amount of parenchyma around the vascular strand of the raph as in Colchicum seed. 5- Wing It is an extension of the testa in the form of a membranous fold as in Pinus or in the form of plume of hairs at the summit as in Apocynaceae or at the base as in Salix or at both ends of the seed as in Alstonia. The plume is sessile and when borne on a stalk it is termed awn as in Strophanthus.

A- Cardamom (illuars). B- Nutmeg (mace). C- Castor seed (caruncle). D- Colchicum seed (strophiole). E- Salix seed (tuft of hairs). F- Argel seed (tuft of hairs). G- Pinus seed (with a wing) .H- Strophanthus seed (awn).a., awn; ca., caruncle.

A- Cardamom (arillus) .B- Nutmeg (mace) .C- Castor seed (caruncle). D- Colchicum seed (strophiole). E- Salix seed (tuft of hairs) .F- Argel seed (tuft of hairs). G- Pinus seed (with a wing) .H- Strophanthus seed (awn).a., awn; ca., caruncle.

Structure of the Seed Testa: Developed from the integuments of the ovule. The Embryo: Developed from the fertilized ovum. The Endosperm: Surrounding the embryo and developed from the primary endosperm nucleus of the embryo sac. The Perisperm: Formed from nucellus. The Kernel Contain of all the tissues of the seed endosed within the testa. It may be formed of the embryo alone or of embryo surrounding by endosperm or persisperm or both.

Exalbuminous: In which the kernel consists of an embryo alone e.g. mustard. Albuminous: In which the kernel consists of an embryo and surrounding by endosperm (e.g. linseed, fenugreek, nuxvomica) or both perisperm and of endosperm (e.g. cardamom, nutmeg)

Forms of Embryo A- Incumbent, entire. F- Spiral B- Incumbent, in T.C. G- Coiled.C- Accumbent, entire. H- Orthoplocus D- Accumbent, in T.S. I- Orthoplocus, in T.S.E-Spiral embryo.Cots., cotyledons, En., endosperm, Rad., radicle; T., testa.

5 Forms of Embryo A-Incumbent,entire. B-Incumbent,inT.C.. C-Accumbent,entire. D-Accumbent,inT.S.. E-Spiral embryo. F- Spiral G- Coiled H- Orthoplocus I- Orthoplocus, in T.S Cots., cotyledons, En., endosperm, Rad., radicle; T., testa.