

CULTURES OF UREDINE^E IN 1899.' 



J. CAR T H U R. 



With the exception of the very important results achieved 

 by Thaxter in the study of American Gymnosporangia, together 

 with similar work by Farlow, Halsted, Stewart, and Carver, only 

 a few attempts have been made in America to trace the connec- 

 tion experimentally between the forms of the Uredineae. 



The three stages of the clover rust (Uromyces Trifolii) were 

 shown by Howell to be genetically connected and the two 

 forms of the raspberry rust (Gym?wco?iia interstitialis) by Clinton. 

 A slight amount of work in this line of research, chiefly of a con- 

 firmatory character, was carried out between 1889 an ^ 1898 by 

 Bolley, Stuart, and the writer. The vet unpublished results of 

 Carleton, obtained -as part of the work of the division of vege- 

 table physiology and pathology at Washington, 2 complete the 

 mention of all American efforts in this line that now occur to 

 the writer. 



The cultures made during the present season (1899), herein 

 to be described, were conducted, with the exception of a single 

 trial, under glass in the greenhouses of the Experiment Station 

 at Purdue University, and upon plants in pots, the plants remain- 

 ing under cover until the observations were completed. Material 

 bearing teleutospores of a number of species was collected dur- 

 ing the previous autumn and winter and preserved until needed 

 by tying in loose muslin and placing on the ground out of 

 doors. 



The method generally adopted to secure infection was the 

 same, whether aecidia, uredo, or teleutospores were in hand. 

 The potted plant was first wet with an atomizer, parts covered 

 with a bloom being rubbed with the fingers until the water 



1 Read before the Botanical Section of the Am. Assoc. Adv. Sci., Columbus meet- 

 ing, August, 1899. 



2 Issued as Bulletin No. 16 since the paper was read. 

 APRIL] 268 



