Dr. Smith's Inquiry into the Structure of Seeds. 205 



in the moments of incipient germination, from or through the 

 surrounding soil. Thus the bulk of the seed is increased, and 

 its vital principle stimulated. It bursts its immediate integu- 

 ment, or testa, and in the first place sends forth the radicle, or 

 young root, into the ground. This part being, as Dr. Darwin 

 well observes, most susceptible of the stimulus of moisture, 

 elongates itself in the direction in which it meets with that sti- 

 mulus ; and descending into the earth, while it fixes the infant 

 plant, assumes its own proper function of imbibing nourishment 

 for the future support of that plant. But before any supplies 

 can be thus obtained, considerable demands are made, even by 

 the root itself; and not only an evolution of parts, but likewise 

 an increase of bulk, takes place in the young vegetable. For 

 this necessary purpose a store is prepared in the Albumen, a sub- 

 stance either constituting a separate body by itself, as in grasses, 

 corn, palms, &c, which, from a hard, dry and tasteless mass, 

 changes, by the action of water and oxygen, into a milky or 

 saccharine fluid ; or the same substance is lodged in, or united 

 with, the bulk of another part, next to be mentioned, the Co- 

 tyledon, or, as they are generally of the plural number, Cotyle- 

 dons. As the root is the part stimulated by moisture, the Co- 

 tyledons appear to be most stimulated by air, and they conse- 

 quently raise themselves, for the most part, out of the ground 

 in order to receive it, in the form of seminal leaves, well known 

 to perform, for a time, the functions of real leaves, and even, 

 by the action of light, to assume their green colour. The Albic- 

 men cannot be said to be stimulated, or acted upon as a living 

 body, by the air or gas, which only produces chemical changes 

 in it ; and the destination of this substance being soon accom- 

 plished, it disappears by absorption. Not so the other parts of 

 the seed, one of which becomes the still descending root, the 



other 



