AETIFICIALLY SPKEADING FUNGOUS DISEASES. 55 
gave only the slightest trace of an infection or none at all, while the 
second shaking in four different experiments gave 20, 70, 4, and 
less than 1 per cent as much infection as the first shaking. The 
second shaking is, therefore, very unreliable as compared with the 
first. These field experiments have been supplemented by a micro- 
scopic examination of spore solutions. 
Two hundred red Aschersonia pustules freshly picked in January 
were shaken five minutes in 1 quart of water, the solution poured into 
a clean dish, and the same pustules shaken again in a similar way 
three times. The solutions of the successive shakings were likewise 
poured into separate dishes. Each solution, in turn, was thoroughly 
stirred and the number of spores present in one-tenth cubic centi- 
meter of solution (a very small drop) were counted by means of a 
slide marked into one-tenth square millimeters. The count gave the 
approximate numbers of spores in the successive solutions to be 9,188, 
2,100, 274, and 19, respectively; or 79.3, 18.1, 2.4, and 0.2 per cent, 
respectively. 
Effect of copj^er sprayers on vitality of spores. — It is a well-estab- 
lished fact that fungi are susceptible to the effects of solutions contain- 
ing very small quantities of copper. Consequently, in purchasing 
spray pumps or retainers of any kind for work with white-fly fungi, 
it has been considered advisable on general principles to avoid 
copper and brass parts as far as possible. Numerous experiments 
have conclusively shown that equally good infections can be secured 
whether a copper or a galvanized-iron knapsack sprayer is used, 
provided the spore solution is not permitted to remain in the tank 
longer than is necessary to spray it into the trees. Throughout the 
summer of 1908 the authors used a copper and a galvanized tank in 
numerous duplicate experiments on different occasions, including 
nearly a thousand trees, and in all these no difference in infection 
secured could be detected. As good infections were secured when 
the copper tank was used as when the spore mixture was applied by 
means of a barrel pump, and as good as resulted in check experiments 
using the dipping and brushing methods where the spore solution was 
carried in a wooden bucket. Unsprayed trees developed no fungus 
except where the natural spread was rapid. 
Effect . of nutrients added to water mixtures of spores. — Experiments 
to determine what benefits, if any, accrue from the addition of nutri- 
ents to the ordinary water solutions of spores were begun in 1906, 
and were continued throughout 1907 and 1908. Agar, glucose-agar, 
glucose, and gelatin were used in varying amounts, and the solution 
allowed to stand varying lengths of time before application. As 
Prof. Fawcett has found a 5.10 per cent glucose-agar solution the best 
medium for the germination of the spores of the red Aschersonia, and 
that germination usually takes place in a little over 24 hours, field 
