12 INVESTIGATIONS OF RUSTS. 



here recorded make it rather certain that Schweinitz and Saccardo are 

 correct. So far as this country is concerned, the writer is convinced 

 that P. tanaceti either belongs almost entirely to tanacetum or does 

 not exist at all. So far it has been utterly impossible, even in a green- 

 house, to make transfers of the uredo from one to another of the 

 numerous supposed hosts of that species, except among, hosts of the 

 same genus/' It is, at any rate, pretty certain that the forms occurring 

 on Vernonia, HeHanthus, Actinella, and Aplopappus. which have been 

 referred to P. tanaceti at various times, should be considered distinct. 



The circumstances connected with the culture experiments with this 

 species were in themselves peculiar. Late in the autumn of 1897 at 

 Manhattan, Kans., it was desired to obtain fresh material of the uredo 

 for inoculating various hosts, but at that date very little else than the 

 teleuto stage could be found. Finally, on October 29 a small amount 

 was found on HeHanthus petiolaris, mixed among a much larger quan- 

 tity of teleutospores, and from this material sowings were made on II 

 pt tiolaris and II. cum uas. On November 8 there resulted one rust spot 

 on the latter host and three on the former. The spots were of the 

 uredo stage, but the interesting feature accompanying this culture was 

 the appearance first of spermogonia in one of the spots. This fact 

 made it probable that a part of the infection resulted from the teleuto- 

 spores of the inoculating material, even at this unusual season for the 

 germination of these spores. On March 7, 1898, w r hile stationed at 

 the University of Nebraska, inoculations of II. petiolaris were again 

 made with the teleutospores only from other plants of the same host, 

 from which numerous spermogonia appeared in eight days, followed 

 shortly by a?cidia, which were fully developed by November 1. By 

 these results the connection of the different stages of the rust is pretty 

 well established. At the same time it is shown that the forms on 

 II. petiolaris and II. amiuus are identical. In all cultures made of 

 this rust both the uredospores and teleutospores have been found to 

 germinate easily and produce infections readily. Reverse cultures 

 with a?cidiospores were not made. 



These experiments were first reported at the 1900 meeting of the 

 Society for Plant Morphology and Physiology, at Baltimore. Since 

 that time Drs. J. C. Arthur 6 and W, A. Kellerman*' have made a 

 number of such experiments, confirming these results, but also seem- 

 ing to indicate a distinction of host forms on different species of sun- 



a Dr. M. Voronin at first also obtained negative results in similar experiments in 

 Eussia in attempting transfers of the rust on to other hosts. (See Bot. Zeitung, vol. 

 30, pp. 694-698, Sept. 27, 1872.) Later he obtained infections of Pucdnia tanaceti 

 from Tanacetum ndgare on sunflower, which, however, did not produce such vigorous 

 growth as ordinarily. (Bot. Zeitung, vol. 33, pp. 340,341, May 14, 1875.) 



''Botanical Gazette, vol. 35, p. 17, January, 1903; Journal of Mycology, vol. 10, 

 pp. 12-13, January, 1904. 



<' Journal of Mycology, vol. 9, pp. 230-232, December. 1903. 



