USE OF THE PLUMULE. 369 



life, of the plant depending upon the development of a 

 true leaf from the plumule. 



It must not be imagined that the process consists, in 

 the first place, of a mere oxidation of the carbon in the 

 seed, a slow combustion by which the spark of life is 

 to be kindled ; the hydrogen of the water plays an 

 important part, and, combining also with the carbon, 

 forms necessary compounds, and by a secondary pro- 

 cess gives rise again to water by combination with 

 oxygen in the cells of the germinating grain. Nor 

 must we regard the second class of phenomena as mere 

 mechanical processes for decomposing carbonic acid, but 

 the result of the combined influences of all the physical 

 powers and life superadded. 



This elongating little twig, the plumule, at length 

 unfolds itself, and the branch is metamorphosed into a 

 leaf. The leaf aerates the sap it receives, effects the 

 decomposition of the carbonic acid, the water, and in all 

 probability the ammonia which it derives from the air, 

 and thus returns to the pores, which communicate with 

 the pneumatic arrangements of the plant, the necessary 

 secretions for the formation of bark, wood, and the 

 Tarious proximate principles which it contains. 



After the first formation of a leaf, others successively 

 appear, all constructed alike, and performing similar 

 functions. The leaf is the principal organ to the tree,; 

 and, indeed, Linnaeus divined, and Goethe demonstrated, 

 the beautiful fact, that the tree was developed from this 

 curiously-formed organ. 



" Keeping in view," says the poet-philosopher, C( the 

 observations that have been made, there will be no 

 difficulty in discovering the leaf in the seed-vessel, not- 

 withstanding the variable structure of that part and its 

 peculiar combinations. Thus the pod is a leaf which is 

 folded up and grown together at its edges, and the capsules 

 ^consist of several leaves grown together, and the com- 



B B 



