THE LEAF. 



CHAPTER VII. 



THE LEAF. 



217. ITS IMPORTANCE. The leaf constitutes the verdure of plants, 

 and is by far the most conspicuous and beautiful 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 and 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 COLOR OP THE LEAF is almost universally green, which of all colors i9 

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

 often finely contrasted with the more delicate 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 coloring 

 which the wildest fancy could scarcely surpass. 



PHYLLOTAXY OR LEAF-ARRANGEMENT. 



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

 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 exactness and beauty, called phyllotaxy (0v/Uov, a leaf, rafjf, order. , 



85 



85, Ladies'-slipper (leaves alternate) ; 8C. Synandra grandiflora (leaves opposite) ; 88, Medeolft 

 Virginica (leaves verticillate) ; 87, Larix Americana (leaves fasciculate). 



