148 RHYTHM 



the whole year, although each individual specimen may only 

 flower for a few days, or, at the outside, for a few weeks. 

 Where the climatic change is slight, trees often shed their 

 leaves at longer or shorter intervals, sometimes as often as 

 six times a year, sometimes only once; and this process is 

 independent of the seasons of the year, so that trees of the 

 same species under the same conditions drop their leaves and 

 acquire new ones at times that do not coincide. This is carried 

 in some cases even further, for we find that in certain trees, 

 for example the orange-tree, the individual branches have 

 become independent of one another, so that on the same tree 

 winter, spring, summer and autumn shoots may be found 

 on different branches. Flowers and fruit may be found at 

 the same time on a tree but on different branches. Plants 

 that live in desert areas have a special adaptation for storing 

 water, and they show a certain irregular periodicity in their 

 size, which is dependent on rare and infrequent rainfall. 



Although there is no winter or summer, spring or autumn, 

 in the tropics, both plants and animals are subject to the 

 periodical rise and fall of the sun and the monthly waxing 

 and waning of the moon. But there is another immense area 

 — and a very densely populated area — of the habitable globe, 

 where even these periodicities are eliminated. In the depths 

 of the sea, two or three thousand fathoms below the surface, 

 we find a very large population of marine animals, and the 

 conditions under which they live are extraordinarily uniform. 



Below about three hundred fathoms the hght and heat of 

 the sun hardly penetrate. Hence, no green plants can live 

 below this limit. Diatoms and algae, which form so large a 

 proportion of the living matter at the surface, cannot live 

 in the absence of sunhght. But the depths are peopled by 

 very large numbers of species of animals of all sorts, and no 

 part of the sea contains a denser population. These deep-sea 

 animals live to some extent on each other, but like other 

 creatures they cannot be self-supporting. They cannot subsist 

 as the inhabitants of the Bermudas, who were said to subsist by 

 "taking in one another's washing." Like the inhabitants of 

 great cities, the dwellers in the depths must have an outside 

 food supply, and this ultimately comes from the surface or 



