144 TWENTY-FIFTH ANNIVERSARY REPORT. 
tissues of the trees is effected through the center of the flowers 
and through the delicate growing tips of branches. An attempt 
was made to learn why some varieties suffer more from the disease 
than others, but with indifferent success. The mode by which the 
disease is normally propagated and spread is more fully stated. 
Some facts are given about the development of the germs in arti- 
ficial cultures, and the chemical and other changes which they 
bring about. In 1886 the proof of the bacterial nature of the dis- 
ease is reviewed and further strengthened, the forms and trans- 
formations of the germs are described and illustrated, and the 
chemical changes they bring about further treated of, including the 
proof that they do not form a poison-in the branches of the trees. 
Statistics and experiments are produced to further show the rela- 
tion of blight to succulency and to explain why the disease varies in 
different varieties of the same kind of fruit. It is further shown 
that the bacteria may live and propagate in common garden soil.” 
The work of the Station on pear scab™’ has had to do almost 
entirely with experiments on its control. Small experiments with 
hyposulphite of soda were made in 1886''8 and with potassium 
sulphide in 1887.18 In 1893 and 1894 extensive spraying experi- 
ments with bordeaux mixture were made in a 42-acre pear orchard 
near Geneva. In the experiments of 1893 information was sought 
on two points :17° (1) The value of dilute bordeaux mixture (1 to 
ir formula) for the prevention of scab; (2) the best number of 
treatments to make prior to blooming. The results of the experi- 
ments furnished satisfactory answers to both questions. By the 
use of dilute bordeaux, scab was kept so well under control that the 
net profit from spraying ranged between $4.77 and $6.10 per tree. 
Three sprayings before blooming gave no better results than two 
sprayings. 
The experiments in 1894 were designed to answer three ques- 
tions 7121 (1) What is the least number of treatments with bordeaux 
mixture (1 to 11 formula) which will practically prevent injury 
from the scab fungus in pear orchards, and at what time in the 
season ought the treatments to be made? 
(2) To what extent is late spraying liable to cause russeting or 
roughness of the fruit? 
™ Venturia pirina (Lib.) Aderh. 
48 Rpt. 5:174 (1886). 
™ Rpt. 6:350 (1887). 
” Bul. 67 (18904); same in Rpt. 12:694-717. ' 
1 Bul. 84 (1895); same in Rpt. 13:649-683. 
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