FACTORS OF INCREASE 115 



tendency to accentuate the reproductive side 

 of the resulting development. If peas are 

 sown, the largest seeds not only give rise to 

 the largest plants, with the greatest weight 

 of pods and of seeds, but to an excess of 

 fruitage when compared with the remainder 

 of the plant ; and in a similar way with other 

 kinds of plants, the largest parent seeds give 

 the greatest returns of fruit and daughter 

 seeds, both absolutely and also in comparison 

 with the growth of leaf, stem and root. It is 

 to be understood, of course, that we are not 

 attempting to deal with single plants, but 

 with sufficiently large numbers to neutralize 

 individuality and small accidents, which some- 

 times produce most unaccountable variations. 

 If we consider the bearing of all the data 

 now brought forward, it seems reasonable internal factors 

 to asi^ume that in the ultimate analysis we 

 are dealing with acquired and inherited tend- 

 encies. In the one case the impulse or stim- 

 ulus to development comes from without ; it 

 is environmental, and acts more strongly up- 

 on the somatogenic portion of the plant, 

 while in the other case it is inherent in the or- 

 gani.-iation of the seed and derived from the 

 parent plant. Whatever the explanation of 

 the origin may be, however, it seems certain 

 that these two opposing factors of increase 

 X3lay an important role in the economy of 



External and 



