196 The Leaf — Its Functions, etc. [May, 



assimilating process of the gases of tlie atmosphere, together with the 

 chemical action above alluded to in the formation of resinous, 

 oliaginous and other matters, necessary for growth maturation and 

 fruiting. And these processes are going on without intermission, 

 from the first formation of the leaf until the seed is perfected, only 

 ceasing, when, from ripening of the fruit, their assistance is no lon- 

 ger required. 



In order that plants shall vegetate vigorously, it is necessary that 

 the soil contain a certain quantity of moisture, as likewise carbonic 

 acid. In the absence of the leaves, as in the germination of the 

 seed, the component substances of the seeds are exclusively employ- 

 ed in the formation of the roots. Each new radical fiber acquired by 

 a plant may be regarded as constituting, at the same time, a mouth, 

 a lung, and a stomach. 



When the leaves, by which it obtains food from the atmosphere, 

 are formed, it probably ceases to derive its carbonic acid from the 

 soil, and during the heat of the summer it receives its carbon almost 

 exclusively from the atmosphere. The power of absorbing nutri- 

 ment from the atmosphere is in proportion to the extent of leaf sur- 

 face, hence every increase in the size and number of leaves is attend- 

 ed with an increase of nutritive power, and a consequent further 

 development of new leaves and branches. And these leaves and 

 branches are accompanied with a corresponding extension and de- 

 velopment of roots and spongelets. Rob a tree of its leaves and you 

 deprive the tree of its means of growth; rob a tree of its roots and 

 you do the same thing. Diminish the leaves by lopping the branches, 

 and you do violence to nature ; truncate the roots and you do the 

 same. Proper pruning must observe strictly these laws. You 

 prune the top to give greater functional power to certain branches. 

 If you prune the root at all, it is to lessen the power of the tree to 

 develop wood and by lessening the vital forces, you thereby develop 

 fruit buds. Such is often effected by a dry season. This year wo 

 find much of the last year's growth has developed fruit buds, which 

 would not have been effected in a wet season. Hence, often, rapidly 

 growing, highly cultivated trees develop no fruit buds. Hence, early 

 fruiting, generally, in dwarfs. 



The function, then, of the leaves and other green parts of plants 

 is to absorb nutritive matter from the atmosphere, and with the aid 

 of light and moisture, to assimilate and appropriate their elements. 

 When the leaves are themselves perfected, they are employed for the 



