16 DIRECTOR’S REPORT OF THE 
to produce an inoculation in any considerable number of young 
alfalfa plants. 
An attempt to supply the ferms by applying pure cultures of Ps. 
radicicola to the seed, drying and sowing, resulted in almost com- 
plete failure, while applying soil from an old alfalfa field at the 
rate of 150 to 300 pounds per acre invariably produced an abundant 
inoculation on these experimental fields. 
Although but 15 of the 67 experimental plats produced a success- 
ful crop of alfalfa without inoculation, 48 of the adjacent plats 
where inoculating soil had been applied produced successful crops. 
That it to say, alfalfa growing, on 33 of the 67 fields which were 
tested, was changed from a failure to a success by the application of 
inoculating soil. These tests are described in detail in Bulletin No. 
300. 
The bacterial flora of cheddar cheese.— A quantitative and quali- 
tative study of the bacterial flora has been made during the ripening 
period in nine normal cheddar cheeses, the work being reported in 
Technical Bulletin No. 8. There was no evident connection be- 
tween the number of bacteria present and the rate at which the 
cheeses ripened. When commercially ripe a cheddar cheese usually 
contains some millions of living bacteria per gram. 
More than 300 pure cultures were isolated and finally reduced to 
33 groups according to the classification of the Society of American 
Bacteriologists. Ten of these groups disappeared from the cheese 
at once; representatives of nine other groups were found in but 
single cheeses, although they persisted there for some time; the re- 
maining 14 groups are the most important members of the cheese 
flora. The Bacterium lactis acidi of Leichmann, which includes 4 
of these 14 groups, is the only species which was always found and 
it practically always included over 99 per cent. of the total germ 
content of the ripening cheese. 
DEPARTMENT OF BOTANY. 
Potato spraying experiments.— During the season of 1907 the 
potato spraying experiments begun in 1902 were continued along 
practically the same lines as in previous years; and the results are 
reported in Bulletin No. 307. In the ten-year experiment at Geneva 
five sprayings increased the yield 73.7 bu. per acre, while three 
spraying increased it 44 bu. In the duplicate of this experiments at 
Riverhead, Lond Island, the gain due to six sprayings was 31.25 bu. 
per acre and to three sprayings 18 bu. In fourteen farmers’ busi- 
