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XV. An Inquiry into the Structure of Seeds, and especially into 

 the true Nature if that Part called by Gartner the Vitellus. By 

 James Edward Smith, M.D. F.R.S. P.L.S. 



Read November 3, 1807. 



Gvertneh, so justly celebrated for his anatomical and physio- 

 logical inquiries into the nature of Seeds in general, and for his 

 particular illustration of One Thousand different kinds, claims 

 the merit of first giving a name and definition to a part called 

 by him the Vitellus, which, though not entirely unobserved by 

 preceding philosophers, had received no particular description 

 nor explanation. Before we enter upon the investigation of this 

 organ, it is necessary to consider the structure and functions of 

 the parts of a Seed in general; and this it will be best to do phy- 

 siologically. 



Three agents are necessary to the germination of seeds, — mois- 

 ture, heat, and air. A seed committed to the ground absorbs, 

 through the vessels of its base, the juices of the soil, or any other 

 moisture that comes in its way ; while it receives, throughout its 

 whole substance, a definite portion of heat, some seeds requiring 

 a greater share of the latter, for the purposes of vegetation, than 

 others. Moisture and heat however are not of themselves suffi- 

 cient to cause the germination of seeds. It has long been known 

 that air is equally necessary ; and modern chemists have ascer- 

 tained oxygen gas to be the particular ingredient of the atmo- 

 spheric air which is requisite, and which is absorbed by seeds, 



in 



