19 



son, of Cornell University, has called attention to the longer time that 

 elapses before spores are formed when certain bacteria are provided 

 with more abundant food material. A customary culture gave a crop 

 of spores in 15-20 hours, a oulture with fewer germs (second dilution) 

 in 36 hours, and one with still fewer germs (third d lution) in 48-72 

 hours. 



The prolificacy of weeds in sterile soil is a matter of common obser- 

 vation. The great ragweed in poor soil produces a crop of seeds when 

 but a few inches high, and the same is true of omer weeds, especially 

 noticeable in normally t til ones. Wild plants rooted in thin soil on 

 rocks often bear single flower s as large as all the remainder of the 

 plant. Analogous development may be seen in smie alpine plants. 



As a summary of the evidence already brought forward it is plain 

 that the environmental conditions of plant existence have a dispropor- 

 tionate 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 ba'h in hot water before sowing, the 

 larger amount of food as when fewer bacteria are plaoed in 

 same amount of culture media, all s iow a favouring action upon the 

 vegetative part greater than obtains with the reproductive part. On 

 the other hand, checking growth by root prunin ? or by keeping plants 

 in undersized pots, reducing the gene al vit tlity by slow diseise, and 

 depriving the plant of sufficient soil and moisture, show a favouring 

 action upon the reproductive part in hastening and multiplying the 

 formation of flower and seed far in excess of the development attained 

 by the vegetative part. 



As a factor to insure perpetuity this law is evidently important in 

 guarding against extermination, for tie poorer the conditions for 

 growth, the m:>re effort the organisms puts forth towxrd seed-bearing. 

 One cannot fail to be impressed by the thought, however, that if this 

 be a general law of nature, it would seem to imply that the weakest 

 and least favourel individuals, being most fruitful, are most likelv to 

 bo perpetuated, which is in evident contradiction to the aeoeptei 

 theory of natural selection and to c unmm observation. 



There is, however, another factor which conns into play here, as a 

 corrective of this tendency to deterioration of the race, and it is to 

 this law that special attentim will now be directel. 



In all the methods of increase in rate of growth, so far brought for- 

 ward, the change has been due in the mun to extern il agencies, and 

 the increased growth was found to be correlated with decrease in amount 

 of reproduction. There are, hovever, m3thois of increase in rite of 

 growth, arising from causes inherent within the organism, that tend 

 in quite a different direction, in fact, are opposed to those already 

 cited The best illustration, and the only one to be given in this 

 article, is tint shown by the size of seeds. It miy be stited as a 

 general \\w that large seeds produce stronger plants with a greater 

 capacity for reproduction than sm%ll seeds of the same kind. 



That larger seeds produce stronger plants, that is, plants possessing 

 both heavier vegetative p*rts and larger yield of fruit, can be shova 

 by abundant experimental data. 



