166 A N £W AND PARASITIC
it is in the latter. They are at once definitely distinguishable from the conldia, and
from the sporangic spores of the Ghoanephora Cunninghamiana (Plate IX, Figs. 13, 14,
20) owing to the fact that one or ordinarily both of the extremities is provided with a
bundle of fine, long, radiant, colourless processes, which in soino cases originate from a
colourless protrusion and in others appear to emerge directly from a point _at which the
epispore is absent (Plate VIII, Fig. 19, Plate IX, Figs. 3, 4, o). They strongly
resemble the rudimeatury mycelial processes of certain of the Rhizidieic and seem to
have a mycelial function as is indicated by the facts that the spores appear invariably
to undergo a veiy considerablo increase in size without ct)ri'espon.ding vacuolation, like
that occurring both in the case of the conidia and in that of the sporangic spores of
Ckoanepliora Cmmipghaviiana, previous to the emergence of germinal tubes, and also that,
in cases wlicre tlioy are cultivared under conditions of defective nutrition, a chlainydosporo
is not unfrequently developed as a direct extension of the intrasporic profoplasm
(Plate IX, Fig. 01. When the latter is the case the parallelism of the spores to
Ilhizidical organisms becomes very striking indeed, because, as will presently be sliown,
the chlamydospores on germinating in most cases give direct origin to sporangiferous
filaments.
The epispore of the spores and that of the conidia, in cases in which the lytter
undergo any considerable increase in bulk ere germinating, is ruptured ere the emergence
of a germinal tube, a phtnoinenoa which does not attend the germination of either the
conidia or spores of Ckoanepkora Cuiminghamima (Plate IX, Figs. 16, ^0). The rupture
does not, however, follow the same course in the two cuses. In that of the spores it
takes the form of irregular fissuring, whilst in tho case of the conidia the epispore is
broken up into a number of distinct fragments (Plate IX, Figs. 3, 4). The occurrence
of rupture of the epispore of the sporangic spores clearly shows that the occurrence
of such a phenomenon in the case of conidia is no just ground for regarding the latter as
parallels of unisporic sporangia; for, if the conidia are to be regarded as such on this
ground, Lhen in a case like tho present the spi>rangic spores must be regarded in the
same light, and this leaves the presence of the mothsr-sporangium unaccounted for.
Even where conidiiibrous filaments produce a single CDiiidium only and the sp<a-angia
become unisporic, as is not uufrequently the case under tho iufluouco of defective nutrition,
the difference between the two forms of fructiiication remains as shai-ply defined as
ever (Plate IX, Figs. 10, 11).
On germinating tho conidia give origin to one, or some times two, germinal tubes,
•which emerge apparently indifferently from any point of the surface. The spores, on. tho
other hand, have never more tlian one tube, and this invariably originates laterally so
«6 to. leave the sites of origin of tiie radiant processes intact (Plate IX, Fig.s. 3, 4j.
When the medium furnishes sufficient nutritive supply, the germinal tubss of both sporangia]
spores and conidia alike rapidly lengthen, ramify, and give origin to a characteristic,
aseptate mucorine mycel'um In cultivations in artificial media the mycelial filaments,
although of considerable magnitude, and as u rule larger than thosj of Ckoujiep/iora
Cunnmg/iamiona ^Plate VIII, Fig. 18; Plate IX, Fig. 14), never attain the colossal
proportions which many of tliein do when tlie plant occurs parasiiically. The mycelium
in artificial cultivations presently gives origin to an apundant crup of .sporangiferous lilainents,
which appcjr first at tf'c margins of the medium and afterwards, as the nutrilive
properties of the latter diminish, ovor its entire surface. In oases whcro liie iiiedium
is highly concentrated a certain number of conidiifcrous lilaim'U.:s are a3s...uiatc'd with
SPECIES OF CHOANEPnOHA. 107
the sporangiferous ones, and in any average cultivation zygospores are liable to'make
thfir appearauco in varying numbers. There is nothing to indicate what is the essentinl
determinant of the appearanco of zygosporfc fructification, for, in two cultivations conducted
side by side in portions of one and the same specimen of a medium, zygospores may
be Entirely absent in one and ahnost entirely replace sporangia in tbo other. When the
medium is a very dilute one chlamydospores alone are produced (Piat3 Vllf, Fi;;. 21).
The phenomena attending the germination of the cldamydospores differs in difreroni
instances. In a certain number of cases they give origin to a mycelium like that originating
fron» the spores and conidia, but in many instunccs no myceHum is formed and the
germinal tube elongates directly into a spnranaifcrous filament (Plate IX, F)gs. 7. 9).
When the nutritive medium is not excefsively poor, two or more chlamydospores may bo
formed in the course of individual mycelial filaments., but, when tho nutritive properties
of the medium fall very low, each conidiuni or spore only gives origin to a single
chlamydospore, and this in many cases is directly continuous with the parent body and
forms a simple extension of the latter (Plate IX, Figs, 5, 6),
The zygospores vary considerably in structural details even within one and the same
culture. In certain oases they are quite typically zygosporic, the two conjugating tubes
which contribute to their formation being of equal value, alike in sizo and general appearance
iPIate Vlir, Figs. 4, 5, 8); in others one of the conjugating elements is much
larger than the other, the difference between them in certain cases becoming so excessive
that in this respect the process comes to be rather of an oospt.ric than a zygosporic
type (Plate VIII, Figs. G, 7, 9, 10), an i in a few cases the spore appears (o be
of a truly azygosporic character and the product of a single mycelial process only (Plate
VIII, Fig. 11). In some instances the conjugating processes take origin irom the
same mycelial filament, in others from distinct ones, and whilst in somo cases they are
unaccompanied by any other peculiar processes, in others they are iissociatod with varying
numbers of short, often twisted processes (Plate VIII, Figs. 6, 8), although thoso
mm hers as to givo rise to the formation of the complicated
which are "ccasionilly associated with the zygospores of
Another point of diffuronco in the
latter species is that the oospi>ri(
and their subsequent investme'T
Cunnùiffhamiaiia (Plate
never are present in such
Rclerotioid masses of tissi
C/ioanephora Ctinnuiff/inmiana
sent as compared with th
from tho wall of the spo:
which is so frequent in CAoaiip-pho,
appears to <iccur here.
The colour of the contents of the conjugating processes
¡ygitsporos in the presepiration
shades of yellow to strong relidish, and not unfrequently, at a ti
of one process have already been completely accumulated termii
the formation of a partition, those of the other are present througli
oT the contents
; witii a special mcnibrano
IX, Figs. 21, 22) novelvaries
from different
me when the contents
lally and separated by
_ )ut its entire course
and continuous with those of the parent mycelial filament (Plate VIII, Fi-r. 7). Tho
mature zygospores are of a deep brown or almost black colour and have average diameters
of 0-037 num. They rarely contain any massivo accumulati'm of oil in the form of
a large globule, but, where sucli a body is present, it can bo readily determined tliat
the epispore, like that of the sporangial spores and conidia, is finely striate (Plae
VIII, Fig. i)!. •
The germination- of the zygospores has not yet been observed, but, judging from
ihe fact that the chlamydospores give direct origin to sporangic fructificatioa whil.-t
those of C/ioanephora Cmniiwiami'ma produce a conidia! one, it- iipptara probable that
ihey are the source of sporangia also.