430 The Living Plant 



kept watered, warmed and lighted uniformly over its whole sur- 

 face. This is something which the reader can readily try for 

 himself, and I commend it to his favorable attention. As the 

 plants come up, the differences they exhibit in rapidity of ger- 

 mination, in the rate of subsequent growth, and in every detail of 

 their structure, are most striking, as the accompanying pictures, 

 traced from photographs, to some extent illustrate (figure 176). 

 In their main features, it is true, those by which we distinguish 



Fiu. 17(5. Young seedlings of String Bean and of Corn, grown from seeds as nearly alike 

 in all visible features as possible, and planted exactly alike. Traced from a photograph. 



them, plants of the same species are alike, but in their details 

 they are always different, and often conspicuously so. Plants of 

 the same kind are, as it were, alike in general but different in 

 particular. The matter is sometimes expressed in this way, that 

 no living being is just like any other living being, a statement 

 impossible of logical proof, but shown by experience to be true 

 for all practical purposes. 



Turning now to a more exact examination of these differences, 

 or variations, we find that they arise from diverse causes. A 

 part of them are of purely mechanical origin, being forcibly im- 

 posed upon some individuals, but not others, by overcrowding, 

 attacks of enemies, or lack of suitable nourishment. Thus, in- 

 sufficiency of water causes the dwarfing of plants simply because 

 they have not enough water with which to grow big; and man can 

 make individual plants short-stemmed in this way if he wants to. 

 Another part of the variations arise from the remarkable power 



