STRUCTURAL BOTANY. 71 



naceous, as in Colutea. In other cases it thickens and be- 

 comes either hard and drj, or fleshy, and sometimes pulpy, 

 Not nnfrequently the pericarp consists of two or more 

 layers of different texture. When there are two such 

 layers, they may be distinguished as Exocarp, outer layerj 

 and Endocarp, inner layer. In the drupe we call the 

 exocarp sarcocarp., and the endocarp putamen. When 

 there are three layers of the pericarp, we call them, begin- 

 ning from the outside, epica/rp, mesocarp, and endocmp. 

 A drupe is indehiscent ; and so are also many dry fruits, 

 particularly one-seeded ones. 



139. Seed is the fertilized ovule, and consists of two 

 parts, the seed-coat and the kernel. 



The names, given to the several parts of the ovule, are 

 also applied to the corresponding parts of the seed. The 

 scar left on the face of the seed by its separation from the 

 seed-stalk at maturity, is termed the hilum, as was stated 

 above. The cJialasa and raphe, when present, are usually 

 conspicuous in the ripe seed, as well as in the ovule. The 

 outer integument, answering to the testa or primine of the 

 ovule, is sometimes called episperm, or spermoderm, but 

 more commonly testa; it varies considerably in texture 

 (from papery to bony), and also in form (from its firmer or 

 looser attachment to the nucleus). Not nnfrequently this 

 coat is expanded into a wing, as in Arabis Leavenworthia, 

 SuUivantia, Tecoma, Chelone, etc., or provided with a 

 tuft of hairs at one end (a coma), as in Epilobium and 

 Asclepias, or even clothed all over with long wool, as in 

 Gossypium (the Cotton-plant). The mnev •mteguTnent of 

 the seed, answering to the tegmen or secundine of the 

 ovule, often termed endopUv/ra, but also tegmen, is fre- 

 quently inconspicuous, and sometimes altogether wanting. 

 The terms denoting the position of the seed in the peri- 



