STRUCTURE OF SEED. 191 



brittle nature of the testa causes it to adhere less to the 

 mesosperm than this latter does to the endopleura ; it is 

 on this account, that those carpologists who say that 

 there are but two membranes in the spermoderm, have 

 united under the name of inner coat or hilofer, the en- 

 dopleura and mesosperm. 



The fibres which form the mesosperm generally arise 

 from the hilum, and expand between the two membranes 

 of the spermoderm ; they fulfil two offices, and are, per- 

 haps, of two different natures ; the one kind, which may 

 proceed from the umbilical cord, may bear nourishment 

 to the embryo and spermoderm during maturation, and 

 when maturity has arrived, may be obliterated; the 

 other kind, which may be directed from all parts of the 

 surface, towards the point of the endopleura where the 

 embryo is situated, may be for the purpose of bearing 

 thither the water absorbed during germination. These 

 two orders of fibres have not as yet been accurately dis- 

 tinguished ; but those which are employed during ger- 

 mination may be observed, by causing large seeds to 

 germinate in coloured water. I have employed those of 

 the Broad Bean, and have very well seen the fibres of 

 the mesosperm become gradually coloured, when intro- 

 duced into cochineal water; I have even seen the colour 

 reach the embryo. In selecting any large seed where 

 the position of the chalaza may be different from that of 

 the hilum, we might decide, by direct experiment, the 

 as yet obscure problem of the nature and direction of 

 the fibres of the mesosperm. 



The portion of the seed where the testa is absent is, 

 as we have said, the hilum ; here we may distinguish 

 two parts : the one, situated near the margin, is a little 

 depression which Turpin has called the Micropyle, 

 which is, according to him, the trace of the place where 

 the branch of the pistillary cord entered ; the other, 



