1894,] Neo-Lamarckism and Neo-Darwinism. 671 
hypothesis itself must admit—then why cannot the soma-plasm 
directly influence the germ-plasm ? 
Again, I wish to point out that modification and evolution 
of vegetable species may and does proceed wholly without the 
interposition of sex—that is, by propagations through cuttings 
or layers of various parts. This proves either one of two 
things—that the germ-plasm is not necessary to the species, or 
else that it is not localized but distributed throughout the en- 
tire body of the individual, as I have shown above; and either 
horn of this dilemma is fatal, it seems to me, to Weismannism. 
If the germ-plasm is not necessary to this reproduction, then 
we must discard the hypothesis of the continuity of the germ- 
plasm ; if the germ-plasm is distributed throughout the plant, 
then we are obliged to admit that it is not localized in germ- 
cells beyond the reach of direct external influences. 
This sexual propagation of plants has been brought to Weis- 
mann’s attention by Strasburger, who cited the instance of the 
leaf-propagation of begonia, and said that plants thus asexually 
multiplied afterwards produce flowers and seeds, or develop 
germ- plasm. Weismann meets the objection by supposing 
that it is possible for “all somatic nuclei to contain a minute 
fraction of unchanged germ-plasm,” but he considers the be- 
gonia, apparently, to be an exception to most other plants, in- 
asmuch as he declares that “no one has ever grown a tree 
from the leaf of the lime or oak, or a flowering plant from the 
leaf of the tulip or convolvulus.”  Henslow meets this latter 
statement by saying that this has not been accomplished sim- 
ply because “it has never been worth while to do it. If, how- 
ever, a premium were offered for tulips or oak-trees raised 
from leaf-cuttings, plenty would soon be forthcoming.” What 
Weismann wishes to show is that the begonia is an exception 
to other plants in allowing of propagation from leaf-cuttings, 
although he should have known that hundreds of plants can 
be multiplied in this way, and that—what amounts to the same 
thing—all plants can be propagated by asexual parts, as stems - 
or roots. 
But there is another aspect to this asexual multiplication of 
plants which I do not remember to hayi seen stated i n this 
