438 THE COTTAGE GARDENER AND COUNTRY GENTLEMAN’S COMPANION.— September lfi, 1850. 
BOTANICAL NOTES ON THE MILDEW OF THE VINE AND HOP. 
By tlie Hov. M. J. Berkeley, M.A., E.L.S. 
Tiif. genus Oidium, a name, at tlie present moment, far j 
too familiar in every country where the Vine forms an iin- ! 
portant object of cultivation, contains a heterogeneous mass 
of species of very various affinity, agreeing only in the circum¬ 
stance of the spores, or sometimes merely of the component 
cells of certain threads of the mycelium being arranged 
end to end so as to form little necklaces. Amongst these 
there is a peculiar group, consisting of such species ns 
O. lencoconinm , Tuektrri, Ac., distinguished by their mealy 
appearance, though not constantly of a pure white, and de¬ 
veloped on the green parts of vegetables. In many eases 
this mycelium creeps amongst the large intercellular spaces 
of the under surface of leaves, the moniliferous threads 
making their appearance through the stomata; but this is 
by no means constant or essential, for, as in the Grape 
mildew, though often exhibiting such a mode of growth, 
they are produced with equal luxuriance on parts of the 
plant, where there are either very few or no stomata. 
Another circumstance connected with such species is, 
that, in a, variety of cases they are the certain forerunners of 
different species of Erysiphe. There are, indeed, some of 
these species which have never been observed to be accom¬ 
panied or succeeded by an Erysiphe, and it is possible that 
such may be autonomous, but in the majority of instances, 
of which the Hop mildew is an example, the Erysiphe most 
certainly and constantly follows or attends the Oidinm, 
Under such circumstances it, was natural that a question 
should arise as to the character of this connection, and 
accordingly it has been warmly contended on the one hand 
that the Oidium and Erysiphe are perfectly independent, 
while on the other the. Oidium is regarded as the mere 
mycelium of the Erysiphe, and it has even been hinted, 
though without any sufficient grounds, that the deciduous 
joints of its erect threads may possibly be of sexual im¬ 
portance. As a step towards the solution of ibis question, 
some observations, accompanied by a figure, were published 
by the author of this memoir in the Gardeners’ Chronicle, 
1851, p.2‘27, tending to show that in Erysiphe communis, as 
, produced upon the Garden l’ea, the sporangia really arose 
from the decumbent threads of the Oidinm, and that in such 
a way as not to make it, probable that this is n case of mere 
parasitical growth, but that the myccloid threads of the 
Oidinm actually give birth to the Erysiphe. The illustration, 
if correct, is clearly of great importance; but inasmuch as 
it has not been received with perfect confidence, I am happy 
to give the annexed figure from the observations of Dr. 
riomley, made perfectly independent of my own, which 
completely confirms the views I had taken of tin; matter, 
and sets it almost beyond doubt (Eig. 1). 
The question was in this state when, in the early part of 
1851, a drawing made the previous year by Dr. Plomley, 
| illustrative of the Hop mildew, was hung up in the Crystal 
Fig. 1.—Erysiphe communis from Hop leaves, allowing the origin of the sporangia 
from the decumbent thread* of the mycelium. From a sketch ky i)r. 
Plomley. 
F'g. P. o.—Pyrnidin anil inclosed spores from the 
Erysiphe of Convolvulus nrvensis. 
b. Pyrnidin from that, of Trifnlium protense, Both 
from sketches by Mr. Broome. 
Fig. 2.-*-Pycnidin produced on the monlliform threads of the Oidium of the Hop leaf. 
Dr. Plomley. 
f 
Fig. 4.—Ampelomyces quisqualis, Cctati, 
sketched by Mr. Broome. 
