28 



BOTANY. 



[chap. I. 



through the stomata of the epidermis. BespiraUon. 

 Oxygen is inhaled from the atmosphere through the 

 stomata^ and carbonic dioxide is returned through the 

 same channels to the atmosphere. 



Assimilation. — The water taken in by the roots passes 

 up the xylem portion of the vascular bundles of the 



Fig. 5. Melon leaf. A typical leaf showing the stalk or petiole, and 

 blade or lamina traversed by numerous anastomosing fibro-vascular 

 bundles or veins. 



stem, and from thence into the leaves by their veins j 

 there it unites with the carbonic dioxide taken in from 

 the atmosphere, and the two are chemically changed 

 into starch by the action of the chlorophyll, or green 

 portion of the cell-contents under the influence of light. 

 The formation of starch as above is termed assimilation. 



