I.] THE GROWTH -FORCE 25 



external world, it was, at the same time, developing an 

 internal power. Plants were constantly growing larger 

 and stronger or more specialized. The accnmulation of 

 vital energy is an acquired character, the same as pecu- 

 liarities of form or structure are. It is the accumulated 

 result of every circumstance which has contributed to 

 the well-being and virility of the organism. The gar- 

 dener knows that he can cause the plant to store up 

 energy in the seed, so that the resulting crop will be the 

 larger. Growth is itself but the expression or result of 

 this energy which has been picked up by the way 

 through countless ages. Now, mere growth is varia- 

 tion. It results in differences. Plants cannot grow 

 without being unlike. The more luxuriant the growth, 

 the more marked the variation. Most plants have ac- 

 quired or inherited more growth -force than they are able 

 to use, because they are held down to certain limitations 

 by the conditions in which they are necessarily placed 

 by the struggle for existence. I am convinced that 

 many of the members of plants are simply outgrowths 

 resulting from this growth -pressure, or, as Bower sig- 

 nificantly suggests ("A Theory of the Strobilus in Ar- 

 chegoniate Plants," Annals of Botany, viii. 358, 359), 

 they are the result of an "eruptive process." The push- 

 ing out of shoots from any part of the plant body, upon 

 occasion, the normal production of adventitious plant - 

 lets upon the stems and leaves of some begonias (espe- 

 cially Begonia phyllomaniaca) , bryophyllum, some ferns, 

 and many other plants, are all expressions of the growth - 

 force which is a more or less constant internal power. 

 This growth -force may give rise to more definite varia- 

 tions than impinging stimuli do; but the growth -force 

 runs in definite directions because it, in its turn, is the 



