514 



The Journal of Heredity 





THE INFLUENCE OF ENVIRONMENT ALONE 



Corn of a single variety (Learning dent): at the left, grown well spaced in hills, at the right 

 badly crowded. The heredity of each plot of corn is the same; the striking differences 

 in growth, and marked differences in reproductiv^e capacity which are not seen in the 

 jjhotograph, are therefore solely due to environment. By avoiding the bad environment 

 {i.e., the crowded condition) the grower might have had corn in the plot on the right, just 

 as big and vigorous as that on the left. If, however, he had planted some such variety 

 as Tom Thumb pop corn on the right, it would have remained small no matter how good 

 the environment provided, because of its heredity, which ])revents it from being anything 

 but small. The attempt to disentangle the influences of heredity and environment is 

 one of the most ])er])lexing problems in l)reeding, as in race betterment, Init failure to 

 attempt it leads to disastrous results. (Fig. 13.) 



two 



ing" 



the 



diilcrenccs in external conditions under 

 which they are grown, i. e., to environ- 

 ment or to differences in their parent- 

 age, i. e., to heredity. Figure 13 shows 



plots of a tall variety of "Leam- 

 dent corn, which differ only in 



environment to which they are 

 exposed. Their ancestry is the same. 

 In fact, the kernels with which both 

 plots were planted came from the same 

 ear. The difference in height between 

 the tall plants on the left and the short 

 plants on the right is due entirely to 

 environment. The tall ])lants were 

 planted far a])art in hills, the short 

 plants were crowded. Otherwise the 

 conditions were similar. Crowding is 

 obviously a bad environment which 

 has dwarfed the plants. From another 



view point, abundant room for develop- 

 ment may be considered a good en- 

 vironment which has stimulated the 

 ]jlants to unusual growth. 



The differences between the two plots 

 were more marked than one would 

 judge from the photograph. At the 

 edge of the crowded jjlot the effect of 

 crowding was less intense and it is these 

 plants on the edge which are seen and 

 not the much smaller ones in the worse 

 environment at the center. The crowd- 

 ing affected not only the height but 

 also the re])roductive organs. Except 

 for the more favored i)lants on the 

 margins which bore a few nubbins with 

 scanty kernels, no ears were produced 

 by the crowded plants. The tassels 

 which bear the male organs were less 



