174 
MR. H. MARSHALL WARD OH THE STRUCTURE 
sixteen species. They are parasitic in the mesophyll of the leaves of various plants, 
and are characterised by producing rounded resting-spores as intercalary swellings on 
the very fine, septate, intercellular mycelium ; these spores germinate like those of 
Tilletia. In Tilletia, however, the resting-spores form dense powdery aggregates, 
which is not the case with the more isolated spores of Entyloma. 
Of the various species of this genus referred to above, three are described as occurring 
in the leaves of species of Ranunculus. One of these— Entyloma ranunculi —appears 
to be extremely common in some places, and has a wide distribution ; its resting-spores 
have often been described, and it is regarded by all the authorities as a well-marked 
species. It has, however, so far as I know, not been specially investigated in detail, 
and, in addition to the other facts contained in the following memoir, it is of interest 
to have observed the germination of the conidia for the first time; the infection 
experiments are also new, and consequently important, and they establish beyond 
doubt the relations of the conidia to the Entyloma* 
I now proceed to the description of my own observations, the completion of which 
has been rendered possible by an outbreak of the disease which the fungus induces on 
a large patch of densely crowded plants of Ranunculus Ficaria during the spring and 
early summer of this year; this patch of diseased plants was so favourably situated, 
and the fungus spread so rapidly and in such enormous numbers on it, that I was 
enabled to observe and record some facts of considerable interest respecting the origin 
and spread of the epidemic due to the action of the parasite. Moreover, material was 
to hand in abundance and in excellent condition, and the circumstances were so 
fortunate that it was possible to note day by day the symptoms of the disease, and 
the progress, climax, and decline of the epidemic. I mention this expressly because 
it is not sufficiently recognised how necessary is the study of the diseases of plants in 
the field—clinically, as it were—as well as in the laboratory. 
The patch of Ranunculus referred to above extended some distance along the 
course of a conveniently situated damp ditch : during February and March thousands 
of young fresh green leaves sprang up, and in April the ground was densely carpeted 
with them ; the leaves were so closely packed that the ditch appeared full of them. 
The ditch itself runs nearly due north to south, and is only damp as a rule ; it 
becomes filled with water during heavy or continuous rain, however, and the water 
* Witli respect to these conidia, it appears that they have been described at various times as the 
spores of other species of Fungi, and that Winter first suggested their connection with Entyloma. Then 
Schroeter observed conidia in connection with Entyloma serotinmn. (Schroetek, loc. cit., pp. 369 and 438.) 
Winter (‘ Kryptogamen-Flora,’ p. 113) says:—“ Sporidienbildung auf der iebenden Uahrpflanze,” 
which conveys the impression that the resting-spores germinate in the leaf and bear “sporidia” on their 
promycelia. The bodies here referred to are true conidia, however, as is clear from my observations, and 
are developed independently of the resting-spores. Moreover, this is the first time the germination of 
the conidia of an Entyloma has been followed and described ( cf. De Bart, ‘Morphol. d. Pilze,’ p. 194), 
thus placing their connection wilh the Entyloma beyond doubt, and explaining their nature as true 
conidia.—May 5, 1887. 
