Relation to Cultivation . 
409 
subsequent development, the individuals of the same sowing 
of the same seed are exposed to very different conditions 
of life, although every effort may have been made to secure 
uniformity in this respect. And it is these differences of 
external conditions which determine which and how many 
of the seedlings shall develop twisted stems, the seedlings 
belonging, of course, to the proper hereditary breed. 
The plants with the most strikingly twisted stems which 
are selected as the seed-bearers are thus generally those 
which have been the most highly nourished. And as this 
mode of selection is pursued in successive generations, so the 
best-nourished plants have for many years had the best- 
nourished individuals as their ancestors. Thus the influence 
of nutrition accumulates as the generations succeed each 
other. 
I may add that I have made similar observations in the 
case of other plants and of other types of monstrosities. 
D. Summer-Sowings. 
The sowings associated with the observations which have 
been already given were made between the beginning of 
March and the middle of May, and the particular time 
of the sowing was without influence upon the percentage 
of twisted stems. Under proper treatment the plants come 
on so vigorously in the course of the summer that whatever 
differences may have originally existed gradually disappear, 
so that they cannot be detected in the winter or in the second 
summer after the sowing has taken place. 
Dipsacus sylvestris torsus is strictly biennial. In spite of 
careful observation, I have been unable to discover any annual 
individuals. I obtained seeds of D. sylvestris from various 
Botanic Gardens and made large sowings, but in no case did 
an annual form occur. This is the more remarkable since 
most biennials (such as Beta , Daucus, Oenothera) produce 
numerous individuals which ‘ bolt,’ from which an annual 
