LIFE HISTORIES OF RUSTS. 



17 



surfaces were covered with very fine drops and then phiced under 

 hu'fje bell jai-s for two days. They were then removed from the bell 

 jars to the <2;recnhousc bench. 



In the accompanying diagrams, W, B, O, and R represent wheat, 

 barley, oats, and rye, respectively.^ The succession of inoculations 

 reads from left to right, the original host plant being on the extreme 

 left. The figures in the form of a common fraction following each 

 host plant are used as follows: (1) The numerator shows the number 

 of leaves successfully infected; that is, leaves showing rust pustules. 

 (2) The denominator shows the niuiibcr of inoculated leaves. The 

 fraction ^\, therefore, indicates 7 pustuled leaves out of a total of 33 

 inoculated. Again, the fraction J followed by the word "flecked" 

 indicates that 1 leaf out of 3 was flecked. The term flecked indicates 

 a more or less close approach to the successful parasitism. The 

 abbreviation ''st. fl." means strongly flecked. 



These diagrams show the results of various sets of inoculation 

 expermients with the difl^erent grain rusts, on their own and other 

 hosts, which have been carried on at different times. 



EXPERIMENTS WITH BIOLOGIC FORMS OF STEM RUST. 



Diagrams 1, 2, 3, and 4 present summaries of inoculation experi- 

 ments with Puccinia graminis tritici (stem rust) from wheat. 



Diagram 1. — Summary of inoculation experiments with stem rust from wheat. 



-wi- 



-OS- 



-R 



32 



W 



-B 



-B 



58 

 60 ■ 



-r1- 



^20- 



-wf 



1 ^fi 



-O 5Q> gQ flecked. 



The results indicated in diagram 1 are further summarized in 

 diagram 2, which shows onh' the successful infections: 



Diagram 2. — Summary of the successful inoculations shown in diagram 1. 

 fw. 



B B.etc. 



W 



R. 



B- 



W. 

 R. 



R- 



-R- 



-w- 



-o. 



O. 



1 Except in a few instances the grains usefi in tiiese e-Tperiments were Preston wheat, Manchuria barley, 

 Early Gothland oats, and spring rye, grown in Minnesota. 



88550°— Bull. 216—11 2 



