OOSPORES. 
267 
minates only after a long period of rest, and does not then give rise at once to a 
new mycelium of the ordinary kind; but the inner layer of the cell-wall bursts the 
outer layer and protrudes through it in the form of a tube (Fig. 174 C), which 
immediately developes into a conidiophore that breaks up into a number of conidia 
each of which developes into a new mycelium. This behaviour is evidently analogous 
to the germination of the zygospores of Pajidor'ma, and to that of the oospores of 
CEdogonium and Cystopus hereafter to be described, which do not however produce 
conidiophores, but a number of zoospores which give birth to new individuals. 
The zygospore may therefore be considered as a sporocarp, forming, together with 
its conidiophores, a second generation, only that the carpospores are here precisely 
like the ordinary non-sexual conidia. 
In our present state of knowledge the Zygomycetes may be divided into two 
families : — 
1. The Mucorini, in which the conidia are formed, by free cell-formation, in 
the interior of spherical receptacles. In the genus Mucor the conidia are set free by 
the bursting of the fragile wall of the receptacle, while in Pilobolus this remains 
intact, but when ripe becomes detached at its base and, together with the conidia, 
is thrown to a distance by its elasticity. Mucor Mucedo is one of the commonest 
moulds, being found on fruits, bread, dung, and even in the interior of nuts and 
apples into which the mycelium penetrates. Mucor stolonifer covers in a short space 
of time large pieces of the same substrata, the mycelium putting out long stolon-like 
branches which attach themselves by their extremity, and produce conidiophores with 
black heads. The mycelium can even penetrate through the shell of fresh-laid eggs, 
and form conidiophores within them. Phy corny ces nitens (Fig. 174 B) is distinguished by 
its conidiophores, which are ten or fifteen centimetres in height and of a violet colour. 
Thamnidium bears an ordinary large conidiophore at the summit of each of the long 
stalks, and below these whorls of small branches with very small receptacles containing 
only a few conidia. Pilobolus almost always makes its appearance when fresh horse-dung 
is covered by a bell-glass^. 
2. The PiptoceplialidsB bear a number of stylogonidia on their conidiophores which 
are much branched towards the summit. The two genera described by Brefeld, 
ChcBtocladium and Piptocephalis, are parasitic upon Mucor Mucedo^ the latter being 
represented in Fig. 175. 
CLASS III. 
OOSPORE yE. 
To this class belong all those Thallophytes, whether containing chloro- 
phyll or not, which are reproduced sexually by means of oogonia. An Oogo- 
nium is a cell distinguished by its size and shape ; the contents either form 
a naked primordial cell — the Germ-cell or Oosphere — by simple contraction and 
rounding off within the oogonium, which opens later, or divide into two 
or more portions, which similarly become oospheres. The fertilisation of 
these oospheres is effected by means of motile Anther ozoids produced within 
^ [On Pilobolus crystallimis see Cohn, Nova Acta Acad. Nat. Curios, vol. XV. pt. I. p. 370. — 
Klein in Pringsheim's Jahrb. für wiss. Bot. vol. VIIL] 
