168 A NEW AND PAISASITIO
A special interest appears to attach to this species of Choanephora both because
of its capacity for parasitic existeace and because it contributes additional evidence that
the genus to which it belongs is of a singular^ generalised type ¡showing special points
of atlinity to many other phycomycete and higher fungi.
Parasitism has, of course, long been recognised as occurring among zygomycete
fungi in the genera Piptocephalis, ¿yncephalis and Cliietocladium, but this would appear
to be the first instance in which the occurrence of a zygomycete as a true parasite in n
phanerogamic host has been recorded. It is somewhat difficult to determine whether
tiie parasitism or the saprophytisni should be regard-id as "facultative." If we arc
to accept De Bary's view thit the production of zygospores in one medium rather than
another is the true criterion,* then the parasitism is '-fiicultatiTe," as zygospores certainly
appear to be more readily produced in artificial media than in the tissues of
the host plant. But it appears to be s(>niewh:it questionable whether this be a true
criterion. Oospores and zygospores when produci-d by parasitic oomycete and zygomycete
organisms are in many cases not produced until after the death of the host has
been induced by the parasitism, which would appear to indicate that their production
does not correspond with the presence of maximal nutritional facilities, but is ratlier
indicative of a fail in theso and in the activity of vegetative growth. Simihrly, in the
<iase ol the purely saprophytic Choanephora Cunninqh'i'niaaa zygospores are never produced
until comparatively late in the duration of any culture and at a period when the
nutritive properties of the medium have been in great part expended in providing for
abundant mycelium and conidiiferous fructification. In so far as the Choanephoras are
concerned, the true criterion of the presence of conditions favouring excessive imcritional
activity and vigorous growth is the ex'.eut to which conidial fructification is produced.
Choanephora Cunninghamiana in its normal site on the flowers of Hibkciis rosa-sinemis
primaiily produces nothing but excessive mycelial growth and conidiiferous fructification.
It IS only when the tissues of the flower have been greatly decomposed that
zygospores make their appearance, and they also frequently occur abundantly in
aj.>oeiation with an impoverished conidiil fructification in artificial cultivations in infusions
of Hibiscus petals. When mycelial growtu is very active and vigorous the conidiiferous
fructification reaches its maximal <levelopinent, and it is only when the conditions
providing for maximal mycelial growth and fully developed conidiiferous fructification
are absent that zygosporic fructification begins to appear. Turning to the second
species of Choanephora, no one who lias ever seen the enormous development which
the mycelial system attains within the tissues of Ipomcea rubro-cmrule'i as compared
with that which it presents in infusions of the host-plant or of Hibiscus petals can
entertain any doubt that the nutritional facilities provided by tlie artificial media are
THStly inferior to those provided by the living tissues of the host-plant. But zygospores
appear rarely or never to occur in the tissues of the host-plant when conditions are
most favourable to mycelial extension and enormous production of conidiiferous fructification,
whilst they occur in extreme abundance in many artificial cultivations, and
in these are associated, not with the conidiiferous, but with the sporangic form of
fructification, which in the case of Choanephora Cuaninghamiana can be unequivocally
demonstrated to be one which is associated, not with an excess but a defect of
nutritional activity, being in fact the form of fructification which only appears witli
defective supply of nutritive materials and goes on showing itself until the defect
• VtrgleiclicndB MorpLoiogie uqJ Biologie der i'ilze, L6ii>zig. Isbi, 8. 4U.
SPJiCIES OF CHOANEPHOUA. 169
becomes so great that clilamydospores alone are produced. If, then, we take general
nutritional activity rather than the production of sexual fructification as the true
criterion, the Choanephora described in the present case ought to be regarded as a
parasite endowed with "facultative" sapropbytism, whilst if Dr. Bary's standard be
retained it must be regarded as a saprophyte endowed with "facultative" parasitism.
The phenomena appear to indicate that we have to deal with a transitionary stage
between the pure saprophytism of the other species of Choanephora and pure parasitism,
but one in which adaptation to parasitic existence has advanced ao far thiit nutritional
facilities are present in greater degree in the latter than when the plant occurs as a
sapropliyte.
lu this adaptation to parasitism on phanerogams the plant shows closer affinities to
certain of tiie Oomycetes, such as Peronospora, than it does to any Zygomycets fungi.
In the one species of Choanephora we have to deal with a purely saprophytic organism
retaining characters of more primitive type than those which are present where any
special adaptation to parasitic existence has arisen, whilst in the other parasitism
makes its appearance, not yet of such highly specialised type as to imply adaptation to
one particular host, but yet so far evolved that growth attains its maximum in association
with it. In this respect the genus presents very genyralised characters and forms a
connecting link between the parasitic and saprophytic Phycomycetes. But it does
more than this, as it presents a curiou-^ly large series of affinities to distinct groups, both
of the higher and lower fungi generally. In Ch'<anepho.-a Ounniaghamiana the normal type
of fructification is certainly conidial, for conidinl fructification occurs alone under
conditions of high nutridon, and is the form which is directly derived from the
clilamydospores, whilst sporangic fructification only occurs in association with very defective
nutrition and is of a more or less abortive type. But in the other species conidial
fructification only occurs under conditions of excessive nutrition, and then does not attain
such a high degree of evolution as it does in its ally, wiiilst the sporangic fructification
is developed under most circumstances, attains a high degree of evolution, and is that
which originates direct from the clilamydospores. Tiie former species has thus a speciiil
relation to the conidiiferous series of higher fungi which culminates in the Basidiomycetes,
and the latter to the sporangiferous series cuhuinatiug in the Ascomycetes. Special affinities
to various groups of Phj comycetes are also indicated by the phanerogamic parasitism,
the occasional Peronosporoid fructification, and the Rhizidiigoid character of the sporangial
spores of the species here specially dealt with, and by the markedly oomycete characters
wliich the sexual fructification of both species in many cases manifests. The genus in
fact in a sense appears to form a sort of centre from which various groups of both the
higher and lower fi mgi radiate, and seems, therefore, to bo worthy of very special
attention. In so far as its sexual fruct;ification is concerned it is less specialised than
the Oomycetfs, and in respect to its conidiiferous and sporangial fructifications loss
specialised than the two great groups of higher fungi have become, and it, therefore,
seems to have in a sense retained ancestral characters in remarkably high degree.
Choanephora Simsom, Cunningham, n.sp. Conidia and spores fusiform, with a brown
longitudinally striate epispore; spores provided with radiant terminal processes.
Parasitic on Ipomcea rub)-o-ca:rulea, Hcok., and Zinnia elegans; saprophytic in various
veg.irable infusions, &c.
Calcutta.