46 



THE LEAF. 



CHAPTER VII, 



THE LEAF. 



21'7. 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 ecor.- 

 oray, being the organ of digeation and respiration. 



218. The leaf is ciiaractekized 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 of the leaf is almost universally green, which of all colors is 

 the most agreeable to the eye ; but its intensity varies by infinite shadce, 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 gaietj-, variety, and splendor of coloring 

 which the wildest fancy could scarcely surpass. 



PHYLLOTAXY, OR LEAF-AREANGEMENT. 



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 

 nnexpected exactness and beauty, called phyllotaxy (ii>vl7.ov, a lea^ ru^ir, order.) 



85, Ladies'-slipper (leaves altennite) ; 86. Synandra grandiflora (leaves oppobito); 83, Me.deola 

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



