SUNFLOWER RUST. 11 



demonstrate t\\o iihility of the rust to propiig-ate itself through the 

 medium of tlie <>-erminating seed of the host, and also make it seem 

 probable that this is even the common method of reproduction in the 

 case of its occurrence on Euphorhla dentata. 



It will be noted also that the results of these experiments make it 

 almost certain that the .Ecidium and Uromyces appearing upon the 

 plants are one and the same species, since in every case all stages 

 resulted from planting the rusted seeds, the a'cidium appearing first, 

 then the uredo, and then the teleutospores. If anything was lacking, 

 however, the proof has since been made complete ])y the experiments 

 of Dr. J. C. Arthur, as reported in the Botanical Gazette,'^ in which 

 the uredospores and teleutospores were obtained on EnphorVm nxtans 

 from a sowing of ivcidiospores from other plants of the same host on 

 June 20, 1899. 



As is well known, the Euphorbia rust is widel}' distributed over the 

 United States, occurring on numerous host species, but it is probably 

 most abundant on J£. dentata and Ji. predii. It is a significant fact, 

 bearing upon the ontogeny of the species, that it is also on these two 

 hosts, particularly on E. dentata, that the a>cidium is most common, 

 and that the rust attacks the seed so severely. The seed pods are also 

 affected considerably in the cases of E. lata and E. vmrginata. 



On June 12, 1897, tecidiospores of this rust had germinated very 

 well in water-drop culture after three days, and on June 22, after a 

 two da3's' culture in water of both tlie aH'idium and uredo from 

 EupJwrhla marginata^ the latter germinated sparingly, but the former 

 not at all. In no instance could the teleutospores be germinated, 

 though germination was not attempted very often. 



The writer has collected all three stages of this rust on EuphorMa 



naculata^ E. marginata, E. dentata, E. presUi, E. glyptosjjerma, and 



E. heterophyUa. On E. petaloidea and E. seipylUfolki only the uredo 



and teleuto stages were found, and on E. lata and what was probably 



E. geyeri even the uredo was rarely seen. 



Sunflower Rust {Puccinia helianthl Schw.). 



Although Saccardo rightly regards this species of Schweinitz as 

 quite distinct, and includes with it the ^cidium of ten associated on the 

 same host, in many herbaria the authority of Winter and Burrill is 

 followed in making it a form of Puccinia tanaceti, while the ^Ecidium 

 is commonl}" referred to JEcldiuni componitaruni, a convenient dump- 

 ing ground for numerous uncertain forms. The writer has always 

 considered this disposition of the species to be without any good 

 reason even on a purely morphological basis, and now the experiments 



"Arthur, J. C, "Cultures of Uredineie in 1899," Bot. Gaz., Vol. XXIX, No. 4, 

 pp. 270-271, April, 1900. 



