236 NOTES ON THE TEASELS.
one plant and the spine of the other, as every transition between
them can be found. It would seem that in most cases they are
nourished directly from the fibrous vessels, no other tissue inter-
vening. For instance, in the serrature of the mid-rib—the most
persistent line of prickles in both plants—the epidermis closely invests
a bundle of fibres for the whole length of the leaf. It further seems
that the vitality of the prickles is dependent on the presence of the
growing fibres, and in that respect they may be regarded as secondary
appendages. This will perhaps account for their presence on the
stem of D. pilosus at an early, that is, fast-growing stage.
No functional importance appears to attach to the prickles. We
may, however, safely prognosticate their further development in direct
proportion to the increase of the vigorous tissue on which they
depend. As we have seen that this tissue is such a capricious and
increasing quantity, the plant bids fair to become eventually a spiny
monster.
Any mention of the leaves of D. pilosus would be incomplete
without a special reference to the pair of characteristic leaflets, occur-
ing as before noticed at the back of the main limb. Do these still
exist as relics of an earlier form ? My ignorance of the other
members of the genus will not allow me to discuss that question ;
but I can certainly say that no such appendages ever occur in
D. sylvestris.
Comparing the two British species, it seems to be correct to say
that the one (sylvestris) is vigorous and variable, and tends to depart
from forms which may have been ancestral. The other (pilosus) is
much less vigorous, and shows affinity with forms (Cephalaria and
Scabious) which also may have been ancestral.
[At the reading of the above paper, Prof. Boulger communicated
the following remarks :—
" I am sorry that I cannot get down to the meeting, as I should
have liked to say a few words on Mr. French's paper on Dipsacus. As,
however, you have kindly given me an opportunity of seeing the
paper, I may briefly state what would have been the substance of
my remarks. Generally, I may say that I consider that the chief
mistake of the modern students of the new teleology—the followers of
Mr. Grant Allen, with whom I must class Mr. French—is that they
constantly look for some immediate utility to the possessor in every
detail of structure. In so doing, they often, I think, overlook two
large classes of structures, which I may term ancestral and indifferent
respectively. The first class, the ancestral, includes : (i.) the