W/tHC- 
UNITED STATES DEPARTMENT OF AGRICULTURE 
BUREAU OF PLANT INDUSTRY 
FOREST PATHOLOGY 
Brown University, 
Providence, R. I., 
4 November, 1933. 
Prof. M. L. Fernald, 
Gray Herbarium, 
Cambridge, Massachusetts, 
Dear Fernaldt 
There is one thing that I failed to note yesterday when 
you showed me the Micro-Suraraar lens. That was to take a memo¬ 
randum of the focal length and speed of the lens. Can you drop 
me a card giving these two points? 
We have here at the government laboratory two Micro-Summar 
lenses of E. Leitz manufacture. One is listed at 80 mm. and the 
other 42 mm., both with a speed of F:4.5. It may be these two 
points are not recorded on your lens, or at least not both of 
them. I am not sure that it would be of any advantage to me to 
know the focal length and speed of your lexis but there is a pos¬ 
sibility that it may be from a point of view of experimentation. 
Sincerely, 
JFC:D 
J. FRANKLIN COLLINS, 
SMI OR PATHOLOGIST IN CHARGE, 
