1902 MICROSCOPICAL JOURNAL | 61 
nia. Many of the fungi in this class passed through var- 
ious stages in their life history ; for example, the mildew 
on wheat, which was first developed on the berberry and 
then spread to the wheat, appearing originally as rust, 
and afterwards as mildew, from the mycelium. The Pres- 
ident referred to the absence in this country of any au- 
thor competent to investigate cases suchas this. On the 
Continent, however, the Governments had taken up the 
matter, and the experts who had examined into it had 
found that to check the spread of the disease it was nec- 
essary to collect all the dead leaves and burn them. The 
President had consequently urged upon the fruit-growers 
the necessity of following this recommendation, but had 
only been able to persuade two growers to do so. Both 
of these, however, had found it to be thoroughly effective. 
Professor A. W. Bennet in his remarks enlarged upon the 
absence in this country of investigations into such mat- 
ters by State-paid establishments, and described what was 
being done in the United States, where every State had 
its own experiment station. The President announced 
that the next meeting would be the annual meeting, when 
the officers and council for the ensuing year would have 
to be elected, the nominations for which were then read. 
QUEKETT MicRroscoPpicaL CtuB.—December 20th, 1901, 
Mr. Angus exhibited and described the use of two simple 
apertometers. The first was an ordinary semicircular pro- 
tractor held at the middle of its periphery vertical to the 
stage; at the centre point was fixed a perforated film, 
mounted on glass, parallel with the stage. Riders or 
pointers slid along the are, indicating the angle. The hole 
in the film was focussed by the lens to be tested, and the 
back of the lens examined with a low power, as when the 
Abbe apertometer is employed. The sine of half the angle 
indicated would be the numerical aperture. This appli- 
ance was valueless for measuring immersion objectives, 
