104 l.IVING PLANTS 



are provided with more abundant food mater- 

 ial. A customary culture gave a crop of 

 spores in 15-20 hours, a culture with fewer 

 germs (second dilution) in 36 hours, and one 

 with still fewer germs (third dilution) in 48— 

 72 hours. 



The prolificacy of weeds in sterile soil is a 

 matter of common observation. The great 

 ragweed in poor soil produces a crop of seeds 

 when but a few inches high, and the same is 

 true of other weeds, especially noticeable in 

 normally tall ones. Wild plants rooted in 

 thin soil on rocks often bear single flowers as 

 large as all the remainder of the plant. Anal- 

 ogous development may be seen in some alpine 

 plants. 



As a summary of the evidence already 

 brought forward it is plain that the environ- 

 mental conditions of plant existence have a 

 disproportionate effect upon the two sides of 

 plant life, the vegetative and the reproductive. 

 An increase in available supply of food, as 

 when the farmer fertilizes his fields, an earlier 

 and stronger start in spring as in the case of 

 wheat treated to a bath in hot water before 

 sowing, the larger amount of food as when 

 fewer and fewer bacteria are placed in same 

 amount of culture media, all show a favoring 

 action upon the vegetative part greater than 

 obtains with the reproductive part. On the 



