THE LEAF 71 



sky and earth like normal leaf blades, or to right and left. Do they 

 belong to the class of leaf formations or that of modified stems ? They 

 represent how much stem? leaf? 



Draw the body in question, with enough of the stem to show the 

 position. 



X. THE LEAP 



103. We have seen that as soon as the seedling comes 

 up the cotyledons are spread, and the leaves of the plumule, 

 if already formed, are shortly unfolded to catch the sun- 

 light ; and that even within the first day after emerging 

 from the soil, the leaves of the seedling take on a deep 

 green color, the sign of healthy activity in plants. In 

 buds, leaA^es have been studied in their early stages and 

 in the resting condition ; and it has been seen how both 

 above-ground and beneath-ground leaves are prepared long 

 before they are needed as foliage, and are held in reserve in 

 order that upon the return of warm weather in the spring 

 the plants may begin witli little delay to make new growth. 

 The varied developments of the stem, as rigid shafts of 

 great height, as twining or as climbing stems, have the 

 object of displaying the leaves to the light to the best 

 advantage. All these things point to the activity of the 

 leaf in carrying on vegetable life. 



THE OFFICE OF THE LEAF 



104. The leaf is doubly active in nourishing the plant. 

 In the first place, it absorbs, like the root ; only, while 

 the root takes up liquids and solutions, the leaf takes in 

 gases. Secondly, the leaf is especially the organ in which 

 solar energy is caught and stored by the formation of 

 certain substances. These substances are the food of the 

 plant, — using now the word food in the same sense in 

 which it was used in the chapter on seeds and seedlings. 

 The food formed in the leaf contains energy to be used 

 in growth and motion. 



105. The food provided for the seedling by tlie mother 

 plant is of small amount. Very soon after germination 



