STaUCTURB OF THE SEED. 215 



of the seed. In ortliotropous and anatropous seeds the embryo 

 is usually straight ; in such seeds as are campylotropous it is 

 curved. Whatever may be the form of the seed, the radicle 

 always points to the micropyle and the cotyledons to the 

 chalaza or some point in its vicinity. This important law 

 being remembered, it is only necessary to ascertain the situa- 

 tion of the micropyle with respect to the chalaza on the 

 surface of the episperm, and the character not only of the 

 seed, but the exact position of the embryo within its folds is 

 at once determined without any further trouble. Thus in the 

 orthotropous seed of the nettle, (Fig. 106,) we know that the 

 micropyle is directly opposite to the hilum and chalaza, which 

 is the base of the seed, the radicle therefore points to the apex 

 of the seed, and its plumule to the base, and the embryo is 

 antitrope {anti, opposite, tpertu, I turn,) or inverted. But in 

 anatropal seeds, as in the pansies, (Viola tricolor. Fig. 108,) we 

 see on the surface of the episperm the micropyle close to the 

 hilum or base of the seed and the chalaza at its apex or opposite 

 extremity ; the radicle or base of the embryo therefore points 

 to the base of the seed and its cotyledons to the apex, and the 

 embryo lies in the seed in its natural position ; that is to say, 

 it is erect or homotrope, (o'/toto{, like, and fplrtw, I turn.) In 

 the campylotropal or curved seed, the base is not displaced, the 

 seed curves on itself, and the micropyle approaches the hilum 

 and chalaza, which is still confluent with it; from this we 

 know that the cotyledonary and radicular extremities of the 

 embryo also approach each other, or the embryo is amphi- 

 trope {afifi, around, and *plrtu, I turn), or follows the curva- 

 ture of the seed, (Fig. 109.) 



Let us now examine in particular each of the parts which 

 constitute the embryo. 



