



' 



f 



I 



ORANGE RUSTS OF RUBUS 



J. C. Arthur 



(with one figure) 



Much interest has been taken recently in the short cycle rusts, 

 especially since the startling discovery by Kunkel, 1 4 years ago, 

 that a rust, indistinguishable from the aecia of Gymnoconia inter- 

 stitialis, would produce promycelia. The year following, Fromme 2 

 and the writer demonstrated the telial nature of Aecidium tuber- 

 culatum Ellis and Kellerm., previously treated as a probable 

 heteroecious rust. Kunkel's discovery stimulated researches by 

 Olive and Whetzel 3 upon the short cycle rusts of Porto Rico, 

 leading to the detection of 5 aecidioid forms previously placed under 

 the form genus Aecidium, and of one uredinoid form quite unlike 

 anything heretofore known. 





Kunkel 



embodied 



known, pertaining to the blackberry orange rust and of their 

 probable bearing upon questions of relationship and evolution. He 

 has concluded that there are in the United States two independent 

 but in part similar rusts on Rubus, one a long cycle form, which he 

 identifies with the Gymnoconia inter stitialis of Europe, and the 



other a short cycle form, for w] 

 nitens, first riven bv Schweinitz 



name 



Carolina* 



No clear morphological characters were found by which to dis- 

 tinguish the short cycle form from the aecia of the long cycle form, 

 although in germination the two behave quite unlike. It is assumed 



1 Kunkel, L. O., The production of a promycelium by the aecidiospores of Caeoma 

 nitens. Bull. Torr. Bot. Club 40:361. 1913; see also Amer. Jour. Bot. 1:37. 1914. 



2 Fromme, F. D. and Arthur, J. C, A new North American Endophyllum. Bull. 

 Torr. Bot. Club 42:55. 1915. 



3 Olive, E. W. and Whetzel, H. H., Endophyllum-like rusts of Porto Rico. Amer. 

 Jour. Bot. 4:44. 1917. 



4 Kunkel, L. O., Further studies of the orange rusts of Rubus in the United States. 

 Bull. Torr. Bot. Club 43 1559. 1916. 



Soi] 



[Botanical Gazette, vol. 63 



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