THE WATER-LILY FAMILY 



also *notice that the middle of the leaf, where the stalk joins it, 

 is a little higher than its edges which are slightly waved. This 

 helps the water to run off. If the water were to remain on the 

 leaves, it would hinder the growth of the plant by stopping up 

 the little holes (stomata), through which the plant absorbs carbon 

 dioxide, a gas which, with the aid of water, the plant is able in 

 the sun-light to turn into 

 starch and thus gain the car- 

 bon which forms an essential 

 element in all plants. 



The openings in land plants 

 are more numerous on the 

 lower side of the leaves, but 

 in the Lotus they are all on 

 the top, because the lower side 

 of the leaf rests on the water, 

 and they would be of no use 

 on that side. Put the blade 

 of a leaf under water and 

 blow down the stalk, and you 

 will soon see little silvery 

 bubbles form on the top-side 

 of the leaf: this is the air 

 escaping through the stomata. 



The air can thus communicate with the root-stock and the roots. 

 This is important for the life of the plant. Every living part of 

 a plant must be accessible to the oxygen in the air. Now, the 

 muddy soil in which the Lotus grows, has scarcely any oxygen, 

 as it is used up in decomposing the dead vegetable substances 

 deposited there. It is through the air-channels in the leaf-stalks 

 that the life-sustaining air can penetrate down to the very root 

 of the plant. 



Another point about the leaves is worthy of notice: the lower 

 side is of a darker colour than the upper, the reason for this 

 being that dark coloured things absorb heat better than light 

 coloured ones. (A black coat is much hotter in the sun than a 

 white one.) Now the heat rays which accompany the light rays 



Fig-. 2. — Part of the epidermis of a leaf 

 (200 times enlarged). S. Stomata. 



