104 
MATURE NOTES. 
Salix hevbacea (which was associated with 6". polaris in Devon- 
shire) is now much more widely dispersed, being found not only 
in Arctic regions, as Greenland, but also in Norway, Bex Alps, 
Tyrol, Engadine, Scotland, Wales, North English and Irish 
mountains. 
As might be anticipated, if different environments be the 
cause of diversity of structure, Salix hevbacea proves to be a 
much more variable plant than Salix polaris. Thus in Suther- 
land it is described as growing two feet high, as well as at 
Antrim and Derry ; while at Edinburgh it has acquired a 
prostrate woody form, with a stem two or three feet long and as 
thick as the little finger. Lastly, as showing another influence 
of environment, Loudon says that while S. hevbacea flowers 
before the leaves appear in the wild state, it not only does so 
but again in April as well when under cultivation. 
Hence, while these two species of dwarf willows, S. polaris 
and S. hevbacea, may well be called survivals since the glacial 
epoch, the latter has proved itself capable of varying so much as 
even to lead systematists to question its identity in some cases. 
To repeat, then, the substance of my contention, evolution 
is based on the fact that both extinct and living beings are so 
often linked by graduated series that the notion of descent with 
modification becomes forced upon our acceptance. Then, when 
we see how plants and animals are constantly varying under 
our eyes, when the environment is changed, the alternative 
supposition that each individual gradation in a long series is a 
“ special creation ” becomes really unthinkable. On the other 
hand, many animals and plants have remained constant for long 
periods, either from want of change in the nature of their 
environment, or from some fixity of disposition which renders 
them less pliable, and so thejr have remained as survivals in the 
midst of evolution which has gone on all around them. 
George Henslow. 
[The importance of the point raised by Professor Henslow and the weight 
attached by anti-evolutionists to the instance of Salix polaris may be seen by 
reference to various writings and addresses of Mr. W. Carruthers, F.R.S., Ex- 
President of the Linnean Society, the best known of the English botanists who are 
opposed to the doctrines of evolution. Mr. Carruthers dealt with the subject in 
his “ Presidential Address to the Geological Association in 1S77,” and recurred to 
it in his “ Presidential Address to the Linnean Society in 1890.” The views of 
Mr. Carruthers are highly approved by Sir J. W. Dawson, an American opponent 
of evolution, in his Geological History of Plants, published in the same scientific 
series as Professor Henslow’s Origin of Floral Structures. We shall be glad to 
know whether the anti-evolutionists consider their position shaken when viewed 
from the aspect in which Professor Henslow regards it. — E d., N.N.]. 
