is one of the most remarkable phenomena amongst Fungi,
and without example amongst other plants. I t sometimes,
however, proceeds from a mycelium, and in the end always
gives rise to fruit-cells, and sometimes to spiral tissue, and
is therefore by itself no sufficient reason for excluding these
productions from the rank of vegetables.
The colour of Fungi depends in most cases upon the contents
of the cells, except in those instances where the walls of
the cells themselves are carbonized. These contents are of
almost every colour except a pure green. When green occurs
in Fungi, as in Peziza æruginosa, Agaricus æruginosus, etc.,
it is generally of a metallic hue, or dull and inclined to olive,
as in the green Russulæ.
I notice, in conclusion, under this head, one or two properties
occasionally exhibited by Fungi. The most notable
of these is the luminosity of some species. Agaricus olearius,
for instance, which grows on olive-trees in the south of
France, is so luminous that it is possible to distinguish letters
by its light, and still more luminous species have been found
in Brazil, Australia, and Amhoyna. We are not, however,
without luminous Fungi in this country, hut the phenomenon
is rare, and has been observed principally in imperfectly
developed species. Decayed wood and leaves also are
sometimes luminous, but whether from the presence of fungous
matter or not, is not quite certain.
I am not aware that in these cases there is any accession
of heat, but Dutrochet has observed that more heat is generated
by Boletus mneus occasionally than by any other vegetable.
I t has been asserted that powerful odours are destructive
to Fungi, and especially that of Russian leather; hut I do
not find this confirmed by my own experience, at any rate as
far as regards the instance alleged.
CHAPTER VII.
PEOPAGATION OF EU NG I.
F ungi are propagated by cells, which either separate by
means of a constriction from privileged portions of their
tissue [spores) (Plate 1, fig. 1), or are produced freely [sporidia,)
within certain sacs called asci (Plate 1, fig. 2) or sporangia.
In a few exceptional cases, though attached to the
tips of the fruit-bearing threads, they are surrounded by a
common membrane (Plate 1, fig. 3, 6). Whether the reproductive
bodies, however, be called spores or sporidia, they
have a singular tendency to appear in definite numbers, either
in twos, fours, or multiples of four. Amongst the lower
sporiferous Fungi there is seldom any attempt at arrangement;
but in the higher, the sporophores almost uniformly
have four spicules, and each of these is surmounted by a
single spore. Very rarely there are hut two, and still more
rarely, as in Phallus, the number exceeds four. Amongst the
sporidiiferous Fungi, the most common number of sporidia in
each ascus is eight; where they are very large, this is sometimes
reduced to four, and, on the contrary, sometimes increased
to sixteen, thirty-two, etc. In some cases the number
is indefinite, and, as far as I know, amongst the Vesi-
culiferi always so. The same law does not hold good when