THE CANE 7 



Function of the Leaf. — The leaf is the manufactory of the plant in which 

 the processes of metabolism mainly take place. To begin with, the green 

 tissues of the leaf take up carbon dioxide from the air through the stomata, 

 which in combination with the water transported by the roots and vascular 

 system forms carbohydrates oxygen being returned to the atmosphere. 

 At the same time nitrogenous bodies are formed through the union of the 

 carbohydrates with the nitrates brought up dissolved in the soil water. 

 The compounds so formed are also transported to other parts of the plant, 

 mainly the stalk. A third function of the leaf is the transpiration of water 

 which takes place through the stomata. 



Physiology of the Leaf. — The ph^^siology of the cane leaf has been studied 

 mainly by Went* and by Kamerling^ in Java, the latter extending and 

 modifying some of the conclusions reached by the first named. It appears 

 that cane sugar is the first product of metabolism occurring in the leaf, 



F.G. 6 



but if more carbohydrate is formed than can be transported to the stem, 

 then the excess appears as starch, which is stored during the daytime in 

 the chlorophyll granules. During the night, or even on a cloudy day, the 

 starch is converted into reducing sugars, and in this form is transported 

 to the stem. The presence of large quantities of starch can be demonstrated 

 in leaves cut just before sundown, and, conversely, its almost complete 

 absence can be shown in leaves cut just before sunrise. At the same time 

 an increase amounting to 15 per cent, takes place in the weight of the leaf 

 during the daytime, this increase being lost during the night. Similarly 

 the greater part of the growth of the stem takes place during the night. 



The Root System of the Cane. — On planting an eye of the cane, germina- 

 tion takes place and a single mother stalk forms. The underground portion 

 of the stalk forms itself into a rhizome or woody short-jointed prolongation 

 of the stalk containing at each node a dormant eye. As growth proceeds 



