LIFE HISTORIES OF BUSTS. 



17 



surfaces were covered with very fine drops and then placed under 

 large bell jars for two days. They were then removed from the bell 

 jars to the greenhouse bench. 



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

 barley, oats, and rye, respectively. 1 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 number of inoculated leaves. The 

 fraction y\, 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 

 experiments with the different grain rusts, on their own and other 

 hosts, which have been carried on at different times. 



EXPERIMENTS WITH BIOLOGIC FORMS OP 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. 



vv 64 

 ^ 



32 



B 16 i 



13 



52 



,ls 



■»i 



wf 



■O ^Q> Tq flecked. 



2 10 

 54' 54' 



6 3 



R?o»s st. 



5 



The results indicated in diagram 1 are further summarized in 

 diagram 2, which shows only the successful infections: 



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



rw. 



|B B.etc. 



p -B 



• W. 

 R. 



W 



II. 



o. 



1 Except in a few instances the grains used in these experiments were Preston wheat, Manchuria barley, 

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



88550°— Bull. 216—11 2 



