CHAPTER FIVE 



LEAVES AND THEIR STRUCTURES 



The leaves of plants are generally their most conspicuous part. 

 The prominence of leaves is the natural result of their relation to 

 light. Leaves manufacture food, and sunlight is necessary in 

 this process. In this chapter we shall study the structure of a 

 leaf, and in subsequent chapters we shall discuss the work of the 

 leaves and the processes that take place within these organs of 

 the plant. 



The parts of a leaf. If we examine a leaf closely, we see that it 

 consists of a broad, thin hlade, marked into small divisions by 

 veins. The vein near the middle of the blade is commonly larger 

 than the others and is called the midrib. In some forms of leaves 

 there are several prominent veins, which we may call the princi- 

 pal veins. In general, the smaller veins form a network uniting 

 with the larger ones, and these in turn connect with the midrib 

 or with the principal veins. These large veins are smallest at 



Fig. q. Leaves with prominent stipules : pea, black willow, red clover, Japanese quince, rose. 



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