PARTS OF SEEDS. 



covering composed of two or even three coats. The nutritious 

 vessels of the seed, which come from the trophosperm, ramify in 

 the thickness of this seed-covering, and we usually perceive near 

 the centre of the hilum a minute hole, which gives them a free 

 passage. 



33. The al'bumen, also called perisperm (from the Greek, peri, 

 around, and sperma, seed) or endosperm (from the Greek, endon, 

 within, and sperma, seed) ; the albumen is a body intermediate 

 between the spermoderm and the embryo, which surrounds the 

 latter (embryo) and ordinarily constitutes a depot of nutritive 

 matter. In general it is formed of a kind of cellular tissue, in 

 which is found the fecula, as in wheat; at other times it encloses 

 fatty matter, as in the castor oil plant (palma christi) ; frequently 

 it is very thin, and sometimes it is entirely wanting. 



37. The embryo or essential part of the seed is the rudiment 

 of the new plant which the seed is destined to produce. In 

 plants unprovided with albumen or perisperm, the embryo con- 

 sists of a single kernel or almond, and fills the sperrnoderm. In 

 this case we call it an epispermatic embryo, because it is covered 

 immediately by the epispenn, or internal layer of the spermoderm. 

 But in plants that are provided with an albumen, the kernel is 

 composed of the latter united to the embryo. (In this instance it 

 is termed an endospermatic embryo.} In this latter case the posi- 

 tion of the embryo may vary considerably ; sometimes it is sim- 

 ply applied upon a point of the surface of the albumen, which 

 presents for its reception a little pit (fossette), as in the grain of 

 wheat, or it may be rolled around the albumen so as to envelope 

 it, more or less completely ; it is then said to be extra : at other 

 times it is entirely enclosed in the interior of the albumen, and 

 then takes the name ofintra embryo, as in the castor-oil seed. 



38. We distinguish in the embryo, that is, 

 in the young plant which is still enclosed in 

 the seed, three principal parts ; the radicle, the 

 plumule^ and the cotyledons (figs. 121 and 

 122). 



39. The radicle (fgs. 124 and 125) is the 

 young root, which before germination is al- 

 ways simple, but by development it is more 



or less divided, and constantly tends towards the centre of the 

 earth. 



Explanation of Fig. 122. The seed of a bean : a, the coty'ledons ; ft, 

 the radicle. 



36. What is the albumen ? 



37. What is the embryo ? 



38. What parts are distinguished in the embryo ? 



39. What is the radicle ? 



