118 GENERAL BOTANY 



as can do without much light, and luxuriate in the 

 cool damp air. 



It is in such places too that we find most climbing 

 plants ; so numerous, indeed, are they in most tropical 

 forests, that one rarely sees a tree without some 

 climbing plant hanging from its branches or twined 

 round its stem. By supporting themselves on the 

 sturdier trees these can, with very little expenditure 

 of constructive material, and therefore also of time, 

 reach to considerable heights, and so obtain the neces- 

 sary light and air. Their flowers too can be exposed 

 to the sunshine and to the visits of insects (which 

 as we shall see later, is of great advantage to the 

 race), while their seeds can be scattered from the 

 great height more widely, by wind or birds. 



But in loose sandy soil, where trees cannot grow SO' 

 Avell, and where there is little shade, and too little mois- 

 ture to support a large number of plants, are found 

 those of exactly the opposite kind prostrate and 

 creeping plants. These spread their weak branches 

 along the surface of the ground, and thus save in 

 part the material that would be required to make 

 stiff upright stems. Their leaves are developed not 

 all round the axis, but mostly to right and left, in 

 one plane, and so face upward to the light, at the 

 same time shading the soil and keeping it a little 

 cooler and less dry than it would be if fully exposed to 

 the sun, whereby a little more moisture is available for 

 the plant. Creeping plants, whose branches send down 

 roots on their own account, can spread more widely 

 that those which are merely prostrate, for they increase 

 their supply of water by drawing on a larger area. 



