LETTER OF J. HENRY TO REV. S. B. DOD. 163 



instance) is planted below the surface of the ground in a damp 

 soil, under a temperature sufficient for vegetation. If we examine 

 it from time to time, we find it sending down rootlets into the earth, 

 and stems and leaves upward into the air. After the leaves have 

 been fully expanded we shall find the tuber entirely exhausted, 

 nothing but a skin remaining. The same effect will take place if 

 the potato be placed in a warm cellar; it will continue to grow 

 until all the starch and gluten are exhausted, when it will cease to 

 increase. If however we now place it in the light, it will com- 

 mence tn grow again, and increase in size and Weight. If we weigh 

 the potato previous to the experiment, and the plant after it has 

 ceased t>> grow in the dark, we -hall find that the weight of the 

 latter is a little more than halt' that dt' the original tuber. The 

 question then i-. 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. Alter the 

 leaves have been formed and the plant exposed to the light of the 

 sun, the developed power of its rays decomposes the carbonic acid 

 of the atmosphere, and thus furnishes the pabulum and the power 

 necessary to the further development of the organization. The 

 same i~ 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 source 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 tin/ pabulum from surrounding vegetable matter in process of 

 decay, or in that of evolving power. .V similar arrangement found 

 is in regard to animal organization. It is well known that the egg 

 continually diminishes in weight during the process of incubation, 

 and the chick, when fully formed, weighs scarcely more than one- 

 half the original weight of the egg. What is the interpretation of 

 this phenomenon? Simply that one part of the contents of the 

 shell has run down into carbonic acid and water, and thus evolved 

 the power necessary to do the work of building up the future 



