VOLUME LIII NUMBER 5 
HE 
BOTANICAL GAZETTE 
MAY 1912 
RELATIONS OF PARASITIC FUNGI TO THEIR HOST 
PLANTS 
I. STUDIES OF PARASITIZED LEAF TISSUE 
ERNEST SHAW REYNOLDS 
(WITH NINE FIGURES) 
Various phases of pathologic study have occupied the attention 
of botanists at different times. Before the exciting causes of dis- 
eases in plants were known, the general external appearance of the 
affected organ was described. Later, most of the attention was 
directed toward the discovery of the parasitic organisms which 
cause the derangements, and incidentally the study of the physio- 
logic responses of the host was begun. Within the last few years 
many students of the subject have examined various morphologic 
changes which occur in diseased plants, first dealing almost entirely 
with the gross anatomic appearance, but later making more minute 
histologic and cytologic investigations. Leaf tissue, when invaded 
by fungi; however, has not been thus carefully studied. Moreover, 
comparative studies are always helpful in deciding general prin- 
ciples, and so it is in pathologic morphology. Only as we become 
acquainted with many examples of cytologic and histologic changes, 
shall we be able to approximate the truth regarding the reaction of 
the host plant to parasitic invasion. The practical value of such 
results can hardly be doubted. Woops (92) has written of this 
matter as follows: 
To most successfully combat a disease, we should know the causes that 
contribute to it, and as much about the causes as possible. We should under- 
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