ON FUNGOID DISEASES OF THE VINE, 
71 
“ If there is any difference between the European Oidium 
Tuclceri, and the conidial form of our own Uncinula spiralis, it lies 
in the somewhat smaller size of the latter ; but that could hardly 
be called a specific difference, since Mohl has called attention to 
the fact that the spores of Oidium Tuclicri itself are variable in 
size. What is called Oidium Tuclieri in this country is nothing 
more than the conidia of Uncinula spiralis , and we have 
repeatedly received specimens bearing the former name, which had 
been exhibited at horticultural meetings, and learnedly explained, 
without the slightest reference to the abundant perithecia which 
clearly showed the species to be Uncinula spiralis .” 
We can add but little to this excellent summary of the 
history of the American mildew by Dr. Earlow, except to say that 
the species was technically described by the Eev. M. I. Berkeley, 
in “ Grevillea,” vol. iv., p. 159, and that it differs considerably from 
the species of Uncinula which is common in Britain on Poplars and 
Willows, although that species will convey a good idea of the 
character of the genus to which the above species belongs. It 
should be distinctly observed that Dr. Earlow has no hesitation 
in declaring that the Uncinula spiralis is destructive in its 
character. 
Uncinula americana , Howe.—About the year 1872 Dr. Howe 
described under this name a species of Uncinula found on the 
leaves of Vitis in the United States, and which he regards as 
different from the Uncinula spiralis. Having examined carefully 
authentic specimens of both forms, it may ndt be out of place to 
point out wherein they differ, and also wherein they agree, so as to 
arrive at some conclusion on the disputed point. 
In size the conceptacles are really identical. The fulcra are 
about twice as long, and consequently more flexuose. The curved 
tips are essentially the same. The mycelium and conidia present 
no appreciable differences, and neither the number of sporangia in 
each conceptacle, nor the number of sporidia in each ascus, 
present any points of divergence. The whole difference resolves 
itself into a question of length in the fulcra, for the average 
number of fulcra produced by one conceptacle is about the same. 
It must be conceded that the length of the fulcra in Uncinula spiralis 
is by no means the same in all localities. Comparison of leaves 
from three localities has satisfied us that the average length differs 
in all, and doubtless an extended examination of a long series of 
leaves from numerous localities, or collected in different years* 
