SOME OBSERVATIONS ON THE CHICKWEED. 91
have adduced in comparison there is, so far as I have observed,
never any departure from certain limited habits. Both are pro-
cumbent to a degree, but nothing more. Even 5. graminea,
with its greatly exaggerated internode, only makes one step
upwards to the top of the herbage, where it then spreads out
normally, but there is no geniculated climbing, which is some-
times very self-evident in the case of S. media.
All the plants of the Chickweed, under apparently the most
favourable circumstances, do not show this tendency to climb,
neither do all branches of the same plant. Nor is it confined
alone to stimulated plants, for I have observed it in weakly
specimens, although there of necessity it is an inconspicuous
feature. Moreover I have observed that the tendency to go
upwards is not always induced by overshadowing foliage. I
have seen the stem climb up a perpendicular bank when exposed
to full sunlight, Neither do I observe that in its climbing it
always makes for the light, although doubtless that is the
ultimate design.
These observations, which can be verified by anyone
interested in the matter, if coupled with the known variable
habit that is so familiar to all, show that the species, if not
exactly in an unstable condition, yet has protoplasmic activities
whose action it is not quite possible to forecast. Regarded under
this aspect of extreme variation, and of the tendency to adopt a
fundamentally different habit, it is interesting to note to which
of the current theories of specific change it most nearly responds.
"Natural Selection," if it exists, is apparently of a latent
character. Of "Struggle for Life'' there appears to be none.
"Influence of Environment'' is a powerful factor, but it is by
no means an overmastering one, as many plants seem to escape,
in their tendency to climb, from its influence.