Journal of Proceedings. lxxi
our own specific diseases. We must remember that the sap-flow in
plants is by no means analogous to the circulation of the blood in animals,
and there is an absence of the complex nervous system. A nearer analogy
might be traced in the known specific action of various blisters and
irritants, or in the production of local abscesses, festers, or like simple
humours, from the inflammation set up by the irritating presence of
some foreign substance. Mr. Fitch said that although a firm believer
in the mechanical oval and larval irritation theory, he thought it pro-
bable that the application or removal of pressure, the stimulated growth
to throw off the foreign substance introduced, and other secondary
causes, also came into play. He had referred to the production of
warts, and to make a rough comparison he would instance a hairy
wart in which we found an excessive development of cuticle and an
increased development of the vascular secretory structure, with the
exudation of an abundant quantity of fluid, causing the extra growth
of hairs; compare this with the familiar "Robin's pin-cushion," or
Bedeguar gall of the rose, where we had excessive development and
thickening of cambium tissue and bark with an increased afflux of
nutritive matter, resulting in the enormously developed growth of
leaves, remembering that the so-called "hairs" with which the gall
is covered are really leaves abnormally developed, with scarcely any'
parenchyma between their fibro-vascular bundles. Dr. Pearce must
also remember that we are not yet by any means fully acquainted
with the relationship between the formative stimulus (mechanical or
otherwise) and the supporter of the stimulus; this also answered, or
rather failed to answer, our President's question as to why the galls,
quite constant in themselves, which occur in exactly similar situations
should exhibit such varied forms. Our present knowledge was not able
to give a ready solution to this involved problem, but we know that
there are still many well-known but ill-explained facts in both animal
and vegetable pathology. Mr. Fitch expressed a hope that some of the
structural botanists in the Club would turn their attention to these
important and interesting points.
The analogy between the various skin diseases in the human subject
attributable to fungoid presence, and the numerous varied and well-
marked fungoid vegetable galls, alluded to by Dr. Pearce, stood on a
similar footing, but with a more perfect concatenation. The subject of
the useful chemical properties, remarked upon by Mr. Letchford, was of
true commercial importance, and deserved more attention in this country
than it at present received. The tannic and gallic acids were undoubtedly
more concentrated in the substance of certain oak-galls than in the oak
bark itself; but why we should annually import from £70,000 to £80,000
worth of galls for tanning purposes, while our own large crop of oak
marble-galls is unmarketable except for the manufacture of rustic
baskets and similar trinkets, requires further explanation. Chemical
analysis hardly warrants this neglect of our native galls. Mr. Fitch