DIMENSIONAL VARIATIONS 71 



believes ( Voyage dans ? Amerique meridionale, t. iv.), 

 that cold on one hand, and decrease of pressure on the 

 other, exert an unfavourable influence on growth. 

 But certainly food has a great deal to do with dimen- 

 sional variations. When food is abundant, and easy 

 to get, animals and man are prosperous and attain 

 large dimensions, while when it is scarce they remain 

 smaller. Japanese horticulturists rely in part on this 

 influence of the scarcity of food in their process for the 

 dwarfing of plants. Most persons have seen or at 

 least heard of these diminutive plants of theirs, 

 mostly conifers, such as Thuja > Juniperus, etc., which, 

 while aged 40, 60, 80, 100, or 150 years, are often 

 much less than a yard high, although their relative 

 proportions are well preserved, so that when you look 

 at them it is exactly as if you were looking at a normal 

 large tree through the wrong end of a glass. These 

 dwarfs are the result, in part, of mechanical processes 

 which prevent the spreading of branches, and in part, 

 of a starving process which consists in cutting most 

 roots, and in keeping the plant in poor soil. 

 Many of these Japanese dwarfs may be seen in 

 Europe, and they well illustrate the influence of 

 external conditions on growth and dimensions. Num- 

 erous instances show that plants or animals transferred 

 from unfavourable to favourable conditions, or vice 

 versa, acquire larger dimensions, or, on the contrary 



