The Inherited Effects of Changes 47 
eral generations to produce seeds al of which contain nearly 
the maximum possible food supply. 
Suppose when this condition is attained we reverse the pro- 
cess and plant the seeds under poorer conditions. The first 
crop from such seeds will still be above the original average, 
but not as much above as though they had grown under favor- 
able conditions. Their seeds again will contain less nourish- 
ment, and the second generation will be still smaller on the aver- 
age, until finally the race reaches the lowest level shown by 
fluctuating variations. 
The inheritance of the acquired character in these cases is 
brought about in rather a peculiar way. The favorable exter- 
nal conditions, for instance, act favorably on the body-cells of 
the plant, and the germ-cells are therefore well nourished and 
store up more food: not all to the same extent, but the average 
is higher than in the preceding generation. The next genera- 
tion thus gets a better start, and if the plants are better nourished 
than the average, a similar advance is again made. We must 
not forget that in each generation some of the seeds may be as 
good as the best, but others are not as good. It is the average 
that is improved, and not the best individual seed. 
It may appear from the case just given that the food condi- 
tions determine only the size and vigor of the plant. This is 
not the whole matter, for even the characters of certain parts 
may be changed in a plus or a minus direction, provided they 
are correlated with the condition of nourishment of the plant. 
De Vries cites the case of the poppy, Papaver somniferum. In 
this plant the stamens may be changed into supernumerary or 
accessory carpels by changing the external conditions. The 
number of these carpels may be as great as 150.0r more. From 
the seeds of flowers with an average crown of carpels, plants 
may be reared having many or few of these organs. The more 
favorable the conditions, the more numerous the carpels, and 
vice versa. Poorly nourished plants may have only one or two 
rudimentary or accessory carpels. 
If we select in each generation the most vigorous plants (hav- 
