150 
ON THE PILOBOLIDiE. 
through the intestines unharmed. That they are not con¬ 
fined to grass, however, is seen by the fact that, when the 
dung of a pig fed almost entirely upon meal was taken direct 
from the stye, it also produced an abundant crop after a few 
days’ sojourn under the bell glass. 
The spores of different species, when cultivated artificially, 
exhibit very different powers of germination. Those of 
P. cedipus, for instance, when placed in pure water, emit 
germ tubes within twenty-four hours ; the same thing takes 
place in a damp atmosphere, even while the spores are still 
contained within the sporangium. The spores of P. Kleinii, 
on the contrary, will not germinate in pure water, but only in 
a decoction of dung or other nutrient medium. 
a . —The Mycelium. 
The spores germinate in the ordinary way by the emission 
of one or more germ tubes which branch repeatedly. When 
fully formed, the mycelium consists of a number of continuous 
main filaments, which bear branches of two kinds, (1) long, 
narrow, tapering, much-divided, thin-walled branches, ulti¬ 
mately cut off by a septum, the object of which is to permeate 
the substratum in search of food, and (2) shorter bladder-like 
processes, which appear to be only swellings of the membrane 
of the main filament, from which they are not divided by a 
septum ; these latter are probably intended merely to increase 
the extent of absorbing surface. 
The contents of the mycelium are of five kinds, besides 
the watery cell-sap ; (1) a homogeneous hyaline protoplasm, 
(2) a number of rounded yellow granules floating therein, 
(3) a quantity of a red oil in minute globules, (4) a crystal- 
loidal substance, called by Van Tieghem mucorine, the octahe¬ 
dral crystals of which may be found floating in the cell-sap, 
especially in the later stages of development, and (5) glycogen, 
or animal starch, which may be recognised by the peculiar 
rosy-red tint which it assumes with iodine. The protoplasm 
of the mycelium is, according to Klein and Van Tieghem, in 
continual movement, which, however, it is difficult to observe 
unless large uninjured portions of the mycelium can be 
obtained. This movement is at first of a circulatory character, 
but after a time it manifests a predominant tendency towards 
some particular point. 
At this point a branch appears which is directed towards 
the surface even when the mycelial tube is deeply buried in 
the matrix, and assumes a widely clavate form. Two, three, 
or more of these, which are destined to produce the sporangia, 
may arise on the mycelium proceeding from a single spore. 
