290 JOSEPH HENRY, LL.D. 



to the experiment, and the plant after it has ceased 

 to grow in the dark, we shall find that the weight 

 of the latter is a little more than half of the origi- 

 nal tuber. The question then is, what has become 

 of the material which filled the sac of the potato ? 

 The answer is, one part has run down into carbonic 

 acid and water, and in this running down has 

 evolved the power to build up the other part into 

 the new plant. After the leaves have been .formed 

 and the plant exposed to the light of the sun, the 

 developed power of its rays decomposes the car- 

 bonic acid of the atmosphere, and thus furnishes 

 the pabulum and the power necessary to the 

 further development of the organization. 



"The same is the case with wheat, and all other 

 grains that are germinated in the earth. Besides 

 the germ of the future plant, there is stored away, 

 around the germ, the starch and gluten to furnish 

 the power necessary to its development, and also 

 the food to build it up, until it reaches the surface 

 of the earth and can draw the sources of its future 

 growth from the power of the sunbeam. In the 

 case of fungi and other plants that grow in the 

 dark, they derive the power and the pabulum from 

 surrounding vegetable matter in process of decay, 

 or in that of evolving power.". . . 



"What then is the office of vitality? We say 

 that it is analogous to that of the engineer who 

 directs the power of the steam-engine in the execu- 

 tion of its work." 



"If he had published in 1844, with some ful- 



