OF ENVIRONMENT 119 



every wave of variability and every impress of 

 the environment upon the soma are communi- 

 cated from it to the germ-plasm upon which it 

 becomes forever indelibly engraved. When to 

 this claim there is added the assumption that while 

 the effect of a single external impression may be 

 very shght, its repetition, rhythmically or other- 

 wise, would finally cumulate to produce appre- 

 ciable and lasting effects, we have a conception 

 difficult to prove or disprove, especially since it 

 is a well-established fact that repetition of stimu- 

 lation does give cumulative effects in both irrito- 

 motility and variabihty. The whole question, 

 however, resolves itself into the comparatively 

 simple inquiry as to the physiological connections 

 and correlations of the soma and germ-plasm. 



It is well known that not all of the various 

 organs or tracts of tissue are directly affected 

 alike by any external factor, a result due to the 

 essential differences of the cells composing them. 

 Thus an arid atmosphere or intense insolation 

 would affect leaf activities chiefly, while unusual 

 soil concentrations woxild influence roots only. 

 The various members of the root and shoot are 

 in close correlation, however, and the activity, 

 growth, and mode of development of organs not 

 directly acted upon by the factors mentioned may 

 be profoundly influenced by the altered products 

 of the organs that are affected. Thus the wound- 

 ing of a root is reflected by changes in the shoot, 

 the removal of one of the parts of a compound 



