LIFE HISTORIES OF FAMILIAR PLANTS 



devices to live and hold their own. Thus it is that, 

 when we \isit a well-stocked greenhouse, we find 

 many quaint and curious plant forms that puzzle 

 our understanding. On the greenhouse shelves, 

 standing side by side amid incongruous surround- 

 ings strangely uncouth, these plant novelties have 

 no meaning, simply because they have been 

 gathered from all the corners of the earth where 

 conditions and environment are entirely different. 

 To understand their (to us) unusual forms and 

 quaint structures we have to consider their natural 

 habitat and the conditions under which they live, 

 together with the enemies they have to com- 

 bat. Also, when we observe what appears to 

 us as a quaint plant form, we should remember 

 that it is really not quaint at all, but that its 

 extraordinary features are the outcome of its 

 struggle for existence and represent that form in 

 which the plant has best been able to survive. 



It would be a poor collection of tropical plants 

 that did not include some specimens of the curious 

 Cactus famil5^ Some examples are shown in Figs. 68, 

 69, and 70 (Plates 46 and 47). Most species of this 

 family are natives of California, Mexico, and South 

 America. They grow in arid plains where, after a 

 short rainy season, they are subjected to perhaps 

 several months of unbroken drought. In such 

 quarters the scorching sun shrivels up everything 

 of the nature of thin-textured leaves, hence the 

 cacti have completely dispensed with their leaves, 

 in short, their whole structure has been condensed 

 into one thick, fleshy mass ; the mass assuming 



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