114 



DESCRIPTIVE BOTANY. 



PART I. 



others they alter their character very considerably after 

 germination has commenced ; they then become green, 

 and expand in a form which closely resembles the or- 

 dinary leafy structure. Some cotyledons, however, whilst 

 still in the seed, have the appearance of miniature leaves, 

 are extremely thin, and delicately veined (fig. 23. a) ; 

 and no one could for a moment consider them in any 

 other light, than as these organs in a young and un- 

 developed state. In ma/iy Dicotyledons, the embryo is 

 a cylindrical body, with nothing more than a notch at 

 one end, indicating the position of the cotyledons ; but, 

 in a few species, there is no appearance of any division, 

 and then it is presumed that the cotyledons adhere 

 together ; or rather, if we judge from analogy, that 

 they are entirely abortive. Their stem consists merely 

 of a slender filament which twines itself round other 

 plants, from which it extracts its nutriment by means 

 of suckers provided for this purpose. 



Here and there, we often find a young plant of several 

 dicotyledonous species, which have three, or even more 

 cotyledons, instead of two. The common sycamore 

 (Acer pseudoplatanus} affords frequent examples, where 

 this unusual number appears to have originated in some 

 process of subdivision, rather than by any supernumerary 

 development of these organs (fig. 127.). These devi- 



ations from the usual character, in species where the 

 cotyledons are most frequently two in number, may 

 as a connecting link between them and plants 



