PREVIEW 281 



following year with more workers, that will make money for 

 man, unless some prowling animal robber gets it first. Charles 

 Darwin saw this interrelationship of plant and animal as a chain 

 of happenings when he pointed out that the size of the clover 

 crop in England depended upon the number of cats in a given 

 region. His friend Huxley immediately went him one better and 

 said the clover crop depended upon the number of old maids. 

 When asked to explain, he gave the following chain of events. 

 Old maids keep cats, cats prey upon mice, mice eat bumblebees 

 and also provide them with places to build their nests, bumble- 

 bees pollinate clover, and on this pollination depends the size of 

 the next year's crop. A perfectly logical chain of events ! 



This unit will explain to us some of these interrelationships 

 between plants and animals and may also show us how man some- 

 times interrupts or displaces a link in the chain of interrelation- 

 ships, which results in changing completely the fauna x or flora 2 of 

 a region. The best example of this perhaps is the case of the man 

 in Australia who wanted a bit of watercress to remind him of the 

 old days in bonny England. Today, the rivers of Australia are 

 choked with this same cress, which, having no enemies and finding 

 conditions favorable, has literally overrun the brooks and rivers. 



We cannot fail to see that some animals and plants are fitted to 

 live under conditions totally unsuitable for others. A fish could 

 not live under the same conditions as a lizard, nor would we expect 

 to find seaweeds growing in desert places where cactuses are 

 found. Such things are quite evident, and if we travel in this 

 vast country of ours we shall also find that plants and animals 

 live in more or less different communities, and that there are dif- 

 ferent climatic zones, in which, because of common needs, certain 

 types of animal or plant life are always found. Such zones can 

 be seen particularly well on a mountainside. Any one who has 

 climbed the Katahdin mountain in Maine, or Mt. Washington in 

 New Hampshire, or any 10,000-foot peak of the Rockies or Sierra 

 Nevada, has had the experience of working his way through forests 

 out into an area of stunted trees and finally out on the bare rocks 



1 Fauna (f 6'na) : the animals of a given region. 



2 Flora (flo'rd) : the native plants of a given region. 



