Vol. XXIII Washington, D. C., January 20, 1923. No. 3 
A CYTODOGICAD STUDY OF INFECTION OF BAART AND 
KANRED WHEATS BY PUCCINIA GRAMINIS TRITICI 1 
By Ruth F. AeeEn 2 
Assistant Pathologist , Office of Cereal Investigations , Bureau of Plant Industry , United 
States Department of Agriculture , in cooperation with the California Agricultural 
Experiment Station 
introduction 
With the enormous increase in the work upon plant diseases, the need 
becomes apparent for greater knowledge of the nature of immunity and 
susceptibility to plant disease. Nowhere is this question of greater inter¬ 
est than in the study of the cereal rusts, where the problem of combating 
these diseases is recognized to be largely the task of breeding for rust 
resistance. 
From the early days of Farrer’s (14) speculations concerning the na¬ 
ture of rust resistance, down to the present, the problem has engaged 
the attention of many workers, but much still remains to be learned. 
The problem is being attacked by the geneticist, the chemist, and the 
cytologist. It is from the point of view of the last that the present 
study was undertaken, in the hope of learning something more of the 
actual behavior of the living host cell when attacked by the fungus and 
of the interaction of host and parasite. 
Farrer ( 14 ) attempted to trace some connection between morphologi¬ 
cal characters and resistance, his idea being that a wheat plant with 
small stomata to keep the fungus from entering, or with very heavy 
epidermis through which the spores could not erupt to form pustules, or 
a wheat plant with narrow erect leaves on which the drifting spores could 
not lodge, would tend to be resistant. 
Biffen (3), after careful breeding experiments with varieties of wheat, 
some of which were susceptible to, and others immune from yellow 
striperust, concludes that resistance and susceptibility are quite inde¬ 
pendent of anatomical features, for dissimilar plants may react similarly 
to the disease, and, what is even more conclusive, of two plants, similar 
in all anatomical details, one may be resistant, and the other susceptible. 
Moreover, immune plants were seen to bear small flecks and even abortive 
pustules, showing that the fungus entered, but for some reason was unable 
to develop normally. 
1 Accepted for publication July 21, 1921. 
& 2 The writer makes grateful acknowledgment to Dr. H. B. Humphrey, at whose suggestion the research 
was undertaken, for steady encouragement during the work, and to Prof. W. W. Mackie and Prof. E. B. 
Babcock for numerous courtesies during the progress of the study. 
^Reference is made by number (italic) to “ Literature cited,” pp. 149-151. 
Journal of Agricultural Research. 
Washington, D. C. 
abu 
(131) 
Vol. XXIII, No. 3 
Jan. 20, 1923 
Key No. G-266 
22329—23-1 
