170 BOTANY. 



The seed includes four parts, of which two are never de- 

 ficient. 



THE ARILLUS. 



An expansion of the apex of the funicle around the seed, 

 which is only seen in a few species ; it may be fleshy, pulpy, 

 or even membranous. This, in the Nutmeg, forms what is 

 called the mace. 



THE SPERMODERM OR EPISPERM. 



An organ which is never deficient, which forms the proper 

 tegument of the seed, and is simple or composed of two mem- 

 branes, the testa and the tegmen. The former is the exterior 

 membrane, so called on account of its coriaceous nature ; it 

 is smooth, and absorbs moisture with great facility. The 

 latter is the internal membrane ; it is not smooth, and does 

 not absorb water. 



THE ALBUMEN OR ENDOSPERM. 



An intermediate body, which frequently exists between 

 the embryo and the spermoderm ; it is composed of diverse 

 matters, fleshy, farinaceous, oily, or analogous to horn. In 

 the nut of the Cocoa the milky part is the albumen ; it is 

 visible also in Maize, Rice, &c. 



THE EMBRYO. 



The rudiment of the young plant, protected and nourished 

 by all the envelopes and liquids of which we have spoken. 

 Under the influence of light, moisture, oxygen and heat the 

 plant is developed. This phenomenon is termed germination. 

 The embryo consists of 



THE RADICLE. 



A little simple root, usually fine and pointed, sometimes 

 thick and obtuse, and the length of which varies. In the act 

 of germination the water reaches the radicle first, which is 

 inflated or elongated in diverse ways. 



THE PLUMULA, 



Or young stem, sometimes scarcely visible. In the seed 

 it is composed of two parts, one beneath the cotyledons, the 

 tigclla, the other above, the gemmula. 





