JOllIim OF AfflCETlAL RESEARCH 
Voi,. XXIV Washington, D. C., May 19, 1923 No. 7 
A STATISTICAL STUDY OF THE COMPARATIVE 
MORPHOLOGY OF BIOLOGIC FORMS 
OF PUCCINIA GRAMINIS* 
By M. N. Levine* 
Pathologist, Office of Cereal Investigations, Bureau 'of Plant Industry, United States 
Department of Agriculture 
INTRODUCTION 
Eriksson and Henning (j)® and Stakman and Levine (j^) have shown 
that the urediniospores of the various biologic forms of Puccinia graminis 
Pers. differ considerably in size. Stakman and Levine also have shown 
that the urediniospores of any of the biologic forms become appreciably 
smaller when the rust is grown on fairly resistant host plants or under 
other extremely unfavorable environmental conditions. 
A mathematical analysis of spore measurements in this connection is 
of considerable value. Pearl and Surface (7) say, “It is certain that not 
only are quantitative methods needed in biology, but also that a far 
more serious need is for something of the methodological viewpoint.” 
Rosenbaum (jo) further emphasizes this need by saying “The biometric 
methods therefore furnish a means of extending the descriptive method 
and of expressing quantitatively what investigators have heretofore 
attempted to express qualitatively.” This would seem to have a special 
application in the case of biologic forms, which have always been dis¬ 
tinguished on the basis of their physiologic behavior rather than that of 
their morphologic structure. 
The object of this work was to determine by means of statistical 
studies the morphologic identity, i. e., the limits of variation and the 
biometric constants for length and width, of the aeciospores, uredinio¬ 
spores, and teliospores of the different biologic forms of stem rust. The 
studies described in this paper were limited to Puccinia graminis iritici 
Erikss. and Henn., P. graminis secalis Erikss. and Henn., P. graminis 
avenae Erikss. and Henn., P. graminis phleipratensis (E. and H.) Stak. 
and Piem., and P. graminis agrostis Erikss. It is intended, however, to 
extend the study to a number of the more important forms of the wheat 
stem rust, P. graminis tritici, which recently have been discovered. 
1 Accepted for publication Aug. 21, 1922. Data from cooperative investigations between the Bureau of 
Plant Industry, United States Department of Agriculture, and the Agricultural Experiment Station of 
the University of Minnesota. 
* The author takes great pleasure in making acknowledgment to Dr. E. C. Stakman and Dr. H. K. Hayes, 
plant pathologist and plant breeder, respectively, of the Minnesota station, and agent and collaborator, 
respectively, of the Office of Cereal Investigations, for many valuable suggestions and helpful criticisms. 
* Reference is made by number (italic) to “literature cited,” p. 567 . 
Journal of Agricultural Research, 
Washington, D. C. 
adw 
39364—23-1 
(S39) 
Vol. XXIV. No. 7 
May 19, 1923 
Key No. G-300 
