OX THE STRUCTURE OF SF.r.DS. 



3:*7 



for the cotyledon is really an albumen, a part fundamentally ' 

 distinct in functions from what is proper to a cotyledon. 

 Thus even so conspicuous a family of plants as the orchidea; 

 which the faithful Jussieu confesses were ouly presumed 

 from analogy to be monocotyledouons, or, as he guardedly 

 expresses it, to have " a single-Iobed '6yrcuiUm^V have been 

 shown by Mr. Salisbury, in the eighth volume of our Trans* 

 actions, the only person I believe who has well examined 

 their germination, to have in fact an albumen, but no coty- 

 ledon at all. Nor does such ambiguity or uncertainty be- 

 long to this family alone. Many plants are presumed to be 

 monocotyledonous, chiefly because they grow in the water ; 

 and it is much to be regretted, that this fundamental prin- 

 ciple of all natural systems should in many cases be so ill- 

 established, and very often so extremely difficult to detect 

 or to determine ; which happens in general where its help is 

 most wanted, as I shall presently endeavour to show ; but I 

 must first speak of the more immediate object of the present 

 essay. 



Gaertner asserts the vitellus of seeds to be u distinct from Vitellus. 

 c< the cotyledons as well as from the albumen, and, for the 

 u most part, situate between the latter and the embryo." 

 He considers as its principal diagnostics the three following Its characters 

 characters : " 1st, that it is most closely connected with the ^[^ to 

 u embryo, so as not to be separable from it without injury 

 H to its own substance: 2dly, that notwithstanding this in- 

 u timatc connection, it never rises out of the integuments 

 W of the seed, as the cotyledons usually do, in germination, 

 u so as to become a seminal leaf, but, rather like the al- 

 u bumen, its whole substance is destroyed by the seedling 

 " plant, and converted into its own nourishment : and 3dly, 

 " that if the albumen be likewise present, the vitellus is al- 

 c < ways situate betwixt that and the embryo, iu such aman- 

 " ner, however, that it may be separated from the albumen 

 M with great ease and without injury." For which reasons 

 this able writer considers the organ in question as " allied 

 u on the one hand to the albumen, on the other to the co- 

 M tyledons," but truly distinct in nature from hoth. He 

 proceeds to observe, that " it is of all the internal parts of 

 u a seed the most singular, and by far the most unfre- 



" tiuent." 



Now, 



