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



" it is of all the internal parts of a seed the most singular, and 

 " by far the most unfrequent." 



Now, to consider all these points separately, in the 1st place 

 the Vitellus is not more closely connected with the Embryo than 

 the greater part of Cotyledons are ; according to the figures and 

 descriptions of Gaertner 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 Cotyle- 

 dons, allowed to be such by Gaertner, as in the leguminous 

 plants, and others already mentioned. 3dly, That the Vitellus 

 is situated between the Albumen (if the latter be present as a 

 separate organ) and the Embryo, is only a necessary conse- 

 quence of the more intimate connection between it and the lat- 

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

 precisely true of the Cotyledons and Embryo, as above men- 

 tioned. For these reasons I presume the Vitellus to differ in no 

 respect from the subterraneous Cotyledons already described ; 

 and that its office is to perform the necessary functions relative 

 to air or oxygen, 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 nourishment to the Em- 

 bryo; because this is abundantly supplied by the copious Albu- 

 ?nen of a multitude of seeds whose Vitellus is very inconsiderable, 

 as grasses ; and because 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 un- 

 fold, 



