L 206 ], 



that produce volatile oils. When such leaves are ex- 

 posed in water saturated with oxygene gas, oxygene 

 is given off in the solar light; but the quantity is very 

 small and always limited; nor have I been able to as- 

 certain with certainty, whether the vegetative powers 

 of the leaf were concerned in the operation, though it 

 seems probable. I obtained a considerable quantity of 

 oxygene in an experiment made fifteen years ago, 

 in which vine leaves were exposed to pure water; but 

 on repeating the trial often since, the quantities have 

 always been very much smaller; I am ignorant whe- 

 ther this difference is owing to the peculiar state of the 

 leaves, or to some confervas which might have adher- 

 ed to the vessel, or to other sources of fallacy. 



The most important and most common products of 

 vegetables, mucilage, starch, sugar, and woody fibre, 

 are composed of water, or the elements of water in 

 their due proportion, and charcoal; and these, or some 

 of them, exist in all plants; and the decomposition of 

 carbonic acid, and the combination of water in vege- 

 table structures, are processes which must occur al- 

 most universally. 



When glutenous and albuminous substances ex- 

 ist in plants, the azote they contain may be suspected 

 to be derived from the atmosphere; but no experi- 

 ments have been made which prove this; they might 

 easily be instituted upon mushrooms and fungusses. 



In cases in which buds are formed, or shoots 

 thrown forth from roots, oxygene appears to be uni- 

 formly absorbed, as in the germination of seeds. I 

 exposed a small potatoe moistened with common wa- 



