THE LEAF 75 



but the under surfaces live in constant contact with 

 water. 



It is interesting to observe how the leaves of plants, 

 by their position and arrangement, throw in different 

 directions the water which falls on them as rain. In 

 many plants, as, for example, beet, violet, dandelion, the 

 leaves are so arranged that much of the water which 

 falls on them is directed towards the centre of the plant, 

 moistening the ground near its base, where the main 

 roots are to be found. As the plant grows, the leaves 

 often bend downwards at the tops while still inclined 

 inwards at the base. There is thus a division of the 

 rain, a portion flowing towards the stem, and a portion 

 towards the outer boundary of the plant, a greater area 

 of soil being thus moistened. This may be observed in 

 the sunflower. In many large trees, amongst other 

 plants, practically all the water is thrown away from 

 the trunk, so that there is a dry space beneath the 

 leaves and branches ; water is not wanted there, for 

 there are no young roots to absorb it near the trunks of 

 such plants. Close observation has revealed a relation- 

 ship between the direction and spread of the rootlets 

 and the drainage system of the leaves of a plant. In 

 those plants with widely-spreading roots the water is 

 conducted towards the margin of the plant system (oak 

 and many other trees). In those with bulbous roots, or 

 with closely-tufted rootlets, or with deep, penetrating 

 taproots, the water is commonly conducted towards the 

 centre (violets, beet, lilies). 



A plant breathes, just as animals do, and also 

 obtains a large proportion of its food from the air 



