A SERIOUS LETTUCE DISEASE. 
121 
a cover glass over a ripe disk, then breathing lightly upon it, resulting 
in an immediate and copious discharge of spores upon the cover glass. 
To determine the per cent, of germination of ascospores and the 
toxic effect of copper sulphate, Bordeaux-mixture-filtrate and other 
substances hanging drop cultures were made in lettuce broth, in distilled 
water and tap water, also in various toxic substances. The tests were 
Fig. 25.—Flat showing effects of different coverings upon the development of apothecia. 
I, Not covered; II, covered with heavy manila paper; III, covered with light manila paper; 
IV, covered with unprinted newspaper. 
made by catching spores upon cover glasses by the method described 
above and preparing hanging drops with these, using the solution to 
be tested. The percentage of germination was read when the spores 
ceased to germinate. 
Bordeaux filtrate No. 1 was made by merely filtering freshly pre¬ 
pared Bordeaux Mixture. The residue remaining upon the filter paper 
was then allowed to dry and remain thus one week. It was then washed 
with the least possible quantity of water and this wash water filtering 
through was tested as Bordeauz filtrate No. 2. 
