358 OS TIIE STRUCTURE OP SEEDS. 



These do not Now, to consider all these points separately, in the 1st 

 hoId * place the vitellus is not more closely connected with the em- 



bryo than the greater part of cotyledons are; according to 

 the figures and descriptions of Gartner himself, the fidelity 

 of which must be evident to any one in the habit of using 

 his book, and especially to those who will take the trouble 

 of comparing a few of them with the seeds to which they 

 refer, while in the earliest stage of germination, at which 

 time the relative connection of the parts is best ascertained. 

 2dly, That the vitellus never rises out of the ground, is a 

 circumstance common to it with many cotyledons, allowed 

 to be such by Gartner, as in the leguminous plants, and 

 /. others already mentioned. 3dly, That the vitellus is situ- 

 ate between the albumen (if the latter be present 'as a se- 

 parate organ) and the embryo, is only a necessary conse- 

 quence of the more intimate connection between it and the 

 latter than either of them has with any other part, which is 

 also precisely true of the cotyledons and embryo, as above 

 mentioned. 

 It does not dif- For these reasons I presume the vitellus to differ in no re- 

 fer from the spect from the subterraneous cotyledons already -described;, 

 cotyledons. anu " tnat its office is to perform the necessary functions rela- 

 tive to air or oxigen, till the leaves come forth and assume 

 those functions, in greater perfection, with the cooperation 

 of light. This seems more satisfactory than the opinion of 

 Gaertner, that the organ under consideration affords nou- 

 rishment to the embryo; because tjiis is abundantly supplied 

 by the copious albumen of a multitude of seeds, the viteL 

 lus of which is very inconsiderable, as grasses ; and be- 

 cause it is unphilosophical to recur to two causes, when 

 one is evidently sufficient. In fact, the vitellus^ as far as 

 I can observe, only dwindles away when the leaves unfold, 

 exactly as happens to the subterraneous cotyledons. The 

 game thing very often takes place as speedily in those which 

 rise out of the ground ; the existence of the latter appear- 

 ing to be prolonged in some instances, merely by their nearer 

 approach to the nature of leaves, as in umbelliferous and 

 cruciform plants. Tbe difference of duration is still more 

 evident, and more instructive as to our present purpose, in 

 the leguminous family, between such cotyledons as rise 



above 



