46 



THE LEAF. 



CHAPTER VII, 



THE LEAF. 



217. Its impoetance. The leaf constitutes the verdure of plants, 

 and is by far the most conspicuous and beautifd object in the scenery 

 of nature. It is also of the highest importance in the vegetable econ- 

 omy, being the organ of digestion and respiration. 



218. The leaf is characterized , by a thin ^ijd expanded form, 

 presenting the largest possible surface to the action of the air and light, 

 which agents are indispensable to the life and increase of the plant. 



219. The oolob of the leai is almost universally green, which of all colors is 

 the most agreeable to the eye ; but its intensity varies by infinite shades, and is 

 often finely contrasted with the more dehcate tints of the flower. Towards maturity 

 its verdure is changed, often to the most brilliant hues, as red, crimson, orange, yel- 

 low, giving our autumnal forest scenery a gaiety, variety, and splendor of ooloring 

 which the wildest fancy could scarcely surpass. 



PHYLLOTAXY, OR LBAF-AKKANGEMENT. 



220. As the position of the leaf upon the stem marks the position of the axillary 

 bud, it follows that the order of the leaf-arrangement will be the order of the 

 branches also. The careful investigation of this subject has developed a science of 

 unexpected ezactness and beauty, called phyllotaxy ((jivlikov, a lea^ rofif, order.) 



86, Ladles'-slipper (leaves alternate) ; 86. Bynandra grandiflora (leaves opposite) ; E 

 Tirginica (leaves verticlllate) ; 87, Larix Americana (leaves fasciculate). 



3, Medeolft 



