190 



, in pure azote, in pure carbonic acid, when 

 moistened they swell, but do not vegetate; and if kept 

 in these gasses lose their living powers, and undergo 

 putrefaction. 



If a seed be examined before germination, it will 

 be found more or less insipid, at least not sweet; but 

 after germination it is always sweet. Its coagulated 

 mucilage, or starch, is converted into sugar in the pro- 

 cess; a substance difficult of solution is changed into 

 one easily soluble; and the sugar carried through the 

 cells or vessels of the cotyledons, is the nourishment 

 of the infant plant. It is easy to understand the nature 

 of the change, by referring to the facts mentioned in 

 the third Lecture; and the production of carbonic 

 acid renders probable the idea, that the principal che- 

 mical difference between sugar and mucilage depends 

 upon a slight difference in the proportions of their car- 

 bon. 



The absorption of oxygene by the seed in germin- 

 ation, has been compared to its absorption in produ- 

 cing the evolution of fcetal life in the egg; but this an- 

 alogy is only remote. All animals, from the most to 

 the least perfect classes, require a supply of oxygene.* 



* The impregnated eggs of insects, and even riches, do not produce young ones, 

 unless they are supplied with air, that 'is, unless the foetus can respire. I have 

 found that the eggs of moths did not produce larvce when confined in pure carbonic 

 acid; and when they were exposed in common air, the oxygene partly disappeared/ 

 and carbonic acid was formed. The fish in the egg or the spawn, gains its oxygene 

 from the air dissolved in water; and those fishes that spawn in spring and summer 

 In still water, such as- the pike, carp, perch, and bream, deposit their eggs upon 

 subaquatic vegetables, the leaves of which, in performing their healthy functions, 

 sr&pply oxygene to rhe water. The fish that spawn in winter such as the C 



