86 MANUAL OP NATURB STUDY. 



Frequently the petiole is grooved upon tlie upper 

 surface so tliat the surplus water may be carried to 

 the stalk) or trunk, and hence down the plant, moist- 

 ening its entire surface. If the rain continues un- 

 til the leaves are loaded with water, the petioles 

 bend with the weight, the margin and apex of the 

 leaf gradually straighten and turn downward, allow- 

 ing the water to flow as from a roof, dropping from 

 leaf to leaf, branch to branch, making its way to 

 the very outer edge of the longest limb, from which 

 it pours upon that part of the ground immediately 

 over the finest roots of the tree; thus the leaves, after 

 they themselves are supplied with drink, turn the 

 surplus over to the roots, a very clever act 

 indeed. 



summary: — 



Leaves are used (1) for the assimilation of food, 

 making plant-substance; (2) for transpiration of 

 moisture ; (3) for respiration, breathing in carbon 

 dioxide and throwing out oxygen; (4) for shade, 

 protecting delicate shoots and fruit from heat of sun; 

 (5) for sloping off the rain so that it may fall with- 

 in easy reach of the finer roots of the plant ; and 

 we may add for shading animals and man from the 

 hot sunshine. At least the shade is so utilized for 

 such purposes. Also for medicine, and tea to 

 drink. 



