External and Internal Factors in Evolution 329 
which, according to my view, bring forth beyond a doubt 
adaptive changes.” 
The external influence of climate and of food act only as 
transitory factors. A rich food supply produces fat, lack 
of food leads to leanness, a warm summer makes a plant more 
aromatic, and its fruit sweeter; a cold year means less odor 
and sour fruit. Of two similar seeds the one sown in rich 
soil will produce a plant with many branches and abundance 
of flowers; the other, planted in sandy soil, will produce a 
plant without branches, with few flowers, and with small 
leaves. The seeds from these two. plants will behave in 
exactly the same way; they have inherited none of the 
differences of their parents. Influences of this sort, even if 
extending over many generations, have no permanent effect. 
Alpine plants that have lived since the ice age under the 
same conditions, and have the characters of true high- 
mountain plants, lose these characters completely during the 
first summer, if transplanted to the plains. Moreover, it 
makes no difference whether the seed or the whole plant 
itself be transferred. In place of the dwarfed, unbranched 
growth, and the reduced number of organs, the plant when 
transferred to the plains shoots upin height, branches strongly, 
and produces numerous leaves and flowers. The plants retain 
their new characters as long as they live in the plain without 
any other new variation being observed in them. 
Other characteristics also, which arise from different kinds 
of external influences due to different localities, such as damp- 
ness and shade, a swampy region, or different geological 
substrata, last only so long as the external conditions last. 
These transient peculiarities make up the characters of 
local varieties. That they have no permanency is intelli- 
gible, since they exhibit no new characters, but the change 
consists mainly in the over- or under-development of those 
peculiarities that are dependent on external influences. The 
effect of these influences may be compared to an elastic rod, 
