560 STRUCTURE AND LIFE HISTORIES 
true to white seeds (when selfed 1 ), were crossed with the 
same variety of red bean. In the FI generation each cross 
gave a different color one blue, another black, and the 
third brown. A varied assortment of colors appeared in 
each case in the F 2 generations. 
4. Two varieties of sweet peas, each breeding true to 
white flowers, when crossed gave, in the FI generation, 
nothing but purple-flowered offspring, resembling the wild 
sweet pea. A medley of white, pink, purple, and red- 
flowered plants appeared in the F 2 generation. Numer- 
ous other cases might be cited, all of which would have 
been unsolvable riddles except in the light of Mendelism. 
482. Inheritance and Environment.- Emphasis should 
be laid on the fact that the behavior of any plant, and 
the characters it manifests, are the result of the combined 
influence of inheritance and environment. A bean seed- 
ling is green, not merely because it has inherited chloro- 
plastids, but because it develops in sunlight; without 
sunlight the green color could not come into expression. 
If we vary any factor of environment (temperature, mois- 
ture, illumination, food) the expression of the inheritance 
may be altered, just as truly as though the inheritance 
were changed. The characteristics expressed by any plant 
(or animal) are the result of' the combined action of inherit- 
ance and environment. It is of fundamental importance 
to a man, not only to be "well-born" (eugenics), but also 
to be "well-placed" (euthenics). 
483. Johannsen's Conception of Heredity. The con- 
ception that inheritance, as previously noted, is not the 
transmission of external characters from parent to off- 
spring, but the reappearance, in successive generations, 
1 The pollination of a flower with its own pollen, or with pollen from 
another flower of the same plant, is called selfing. 
