CORRESPONDENCE. 
101 
Mr. Taylor on Black Knot. 
To the JEditor of the ' Monthly Microscopical Journal.^ 
Washington, U.S.A., July 1, 1875. 
Dear Sir, — Your Journal for May 1 has just come to hand. I 
have read with pleasure the remarks of Charles B. Plowright, on 
pp. 209 and 210, relating to my articles on Black Knot and Erysiphe 
Tuckeri. He says of the latter : " Of it in the ascigerous condition 
we have seen no specimens, and therefore offer no remarks, but would 
only suggest that Fiickel, in his ' Symbolee MycologicsD ' places it in 
the genus Sphcerotheca, as a variety of S, Castagnei." As I am not a 
mycologist, but simply an observer, I would be much pleased to have 
the views of the Eev. M. J. Berkeley and Messrs, M. C. Cook and 
C. B. Plowright, and others who have given the subject particular study, 
and to this end will forward by this day's mail* a foreign grape-leafy 
on which about one hundred specimens will be found in good condi- 
tion. I have had it in my possession for several years, and plucked it 
from the grape vine of our foreign collection myself. I would like 
the specimen now sent to be placed first in the hands of Mr. Berkeley, 
as I understand he takes special interest in this subject, and he can 
give such specimens as he desires to others. When I have time I 
will review my experiments on Black Knot, and will forward specimens 
of the asci containing the sporidia on microscopical slide for exami- 
nation in London. 
Faithfully yours, 
Thomas Taylor. 
A Proposed Prize for the best Objective. 
To the Editor of the ' Monthly Microscopical Journal.^ 
Bkighton, July 10, 1875. 
Sir, — There seems to be now no longer any doubt that an object- 
glass to suit all purposes cannot be made. Large angular aperture 
is a necessity for diatom work and the like ; but on the other hand 
moderate aperture is considered best for physiological and scientific 
purposes. The names of Carpenter, Wenham, and Slack suffice to 
settle that point. 
The inducements to make glasses of the first kind are obvious, 
and lie on the surface. They are such as are required by the largest 
portion of the makers' clientelle, the amateurs ; they can be easily 
submitted to imanswerable tests, the resolution of difficult diatoms ; 
and they can be judged of by everybody. Such glasses therefore 
acquire a finer reputation. 
Not so, however, with physiological glasses ; the facts in this case 
are all the other way. Men really doing scientific work are compara- 
tively few, and there is no standard by which the work required * of 
* Specimen lias not arrived. — Ed. ' M. M. J.' 
