3j5 on the structure of seeds. 



Cotyledons. As the root is the part stimulated by moisture, the coty- 



ledons 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 actiou of light, to assume their green co- 

 lour. The albumen 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 accomplished, it disappears by ab- 

 sorption. Not so the other parts of the seed, one of which 

 becomes the still descending root, the other the nurse, or, 

 if we may say so, the foster brother of the young ascend- 

 ing plant, which last originates from the extremity of the 

 embryo opposite to the root, but. always, like that, most 

 intimately connected with the cotyledons. These indeed, 

 sooner or later, wither away; when the acquisition of real 

 and more ample foliage renders them snperiiuous, or no 

 longer necessary. But all cotyledons do not ascend out of 

 the earth, nor assume any of those functions of leaves in 

 which light is concerned. In the horse chesnut, the cyamus 

 nelumbo, the tropmolum majus, and some other plants, they 

 always remain buried, no doubt acted upon by the air or 

 gas alone. Even in plants of the same natural order, pa- 

 pt'lionacece, some, as lupinus, raise their cotyledons into 

 the air and light, in the form of very conspicuous green 

 ■•eed-leaves ; while others, as lathyrus, retain them under 

 ground, concealed in the black skin of the seed, quite out of 

 the reach of every ray of the latter. In these we know r a 

 farinaceous albumen is lodged, whether they rise into the 

 fight or not; and the closest analogy leads us to conclude, 

 that their functions are otherwise similar, which can only 

 be wiia respect to air. 



M t indisnensa- Even cotyledons however are not indispensably requisite 



i»l«*. to a seed, though the albumen appears to be, in some form or 



other, necessary to all seeds. Not to mention the tribes of ve* 

 getables allowed or guessed to be without cotyledons, and 

 thence, for systematical convenience, denominated acotyledo- 



\bsent in nous.; all, who have sufficiently considered the matter, know 



plants called j na ( j n those called roonocotyledonous, what is vulgarly taken 

 moiiocotyledo- * 



ROUS. * * 



