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On the Heteroecious Plant Rusts of Indiana. 



By Aaron G. Johnson. 



In the study of any organism, a knowledge of its life history is one 

 of the things of first interest. Particularly is this true in the study of the 

 heteroecious plant rusts, exhibiting, as they do, alternating phases on 

 entirely different host plants. The complexity, which these plant parasites 

 present, adds varied interest to their study, although the same complexity 

 offers abundant obstacles in determining the connection of the various 

 forms. 



It is the purpose of this paper briefly to show what has been done 

 in the way of connecting forms represented in the State, and what re- 

 mains to be done in this particular line. In presenting the unattached 

 forms, particularly the unattached aecia, it is hoped to help engage the 

 intei'est of others in assisting in any way possible in properly connecting 

 up these forms. The three lists given below show respectively the con- 

 nected forms, with the authorities and dates of connection for each 

 species, the unattached telial forms, and lastly the unattached aeeial 

 forms. The first two tables are based on Dr. Arthur's Revised List of 

 Indiana Plant Rusts (Proc. Ind. Acad. Sci. for 1903.) For convenience, 

 the familiar genus names Uromyces and Puccinia are used, the species 

 names, as far as possible, being revised to date. The third table is based 

 on specimens in Dr. Arthur's herbarium, as are also the aeeial forms ap- 

 pearing in the first table which have been connected up since the pres- 

 entation of Dr. Arthur's list. For host names Britton's Manual (2nd. Ed.) 

 is followed. The sincere gratitude of the writer is here expressed to Prof. 

 J. O. Arthur for access to his very valuable herbarium as well as to his 

 extensive library. Most able assistance was also given throughout by 

 both Dr. Arthur and Mr. F. D. Kern, for which the writer is very greatly 

 obliged. 



The life histories of thirty-four species of heteroecious rusts repre- 

 sented in Indiana are now known. The aeeial stage, however, of nine 

 of this number is not known to occur within the State. In some cases 



