Griffiths: Common Parasite: of Powdery Mildews 185 



ipJi 



produce mature perithecia on account of the depredations of its para- 

 site. It would be interesting to know whether the conidial stage of 

 tlie Erysiphc carries the plant over the winter season or whether the 

 GiiiidcUa becomes inoculated by the same species growing oji 

 other composites in the same locality. It is also interesting to 

 compare this case with the propagation of the conidial stage of the 

 grape mildew in European countries year after year without the 

 intervention of tlie perithecial stage. 



While in company with Mr. T. A. Williams in \\')oming and 

 Montana in 1898, an abundance of this plant was found onGrin- 

 dclia sqiiarrosa and Lygodesmia juncca, especially in the \icfnity 

 of I^uffalo, Wyoming, and Billings, Montana. The specimens col- 

 lected at old Fort McKinney in \^'}'oming show the habits of the 

 parasite the best of any which I have. The Erysiphc on the 

 lower leaves is practically destroyed but that on the upper younger 

 leaves produces perithecia in abundance. The Ampdovivcc'I \?, 

 easily recognized by its dusty appearance which gradual!)- grades 

 off into the characteristic nhitc appearance of the mycelium of 

 the host. In this intermediate region the pycnidia may be found 

 in abundance which develop within the perithecia, and which con- 

 sequcntl)- have a globular appearance. On the lower leaves the 

 pycnidia are usually of the o\'aI or p)-riform t)-pe. This is easily 

 accounted for from the fact that the Ampdoiiiyccs produced its 

 p}xnidia on the lower leaves at a time when there were no peri- 

 thecia formed and did not spread as rapidl}- as the host. The same 

 holds true in general of specimens collected near Buffalo, Wyoming, 

 on Lygodesmia juncca, excepting that the areas affected hy Auipdo- 

 viyccs are more localized and scattered. 



Besides the synonymy given abo\-c' two other species of this 

 genus have been described, /. e., Cifinoholus plautagiuis Oud.. and 



asitinis (Cocc.) Sacc, .specimens of which have not been seen 

 and concerning which, consequent!)-, no positive statements can be 

 made. So far as the descriptions in Sylloge Inmgorum are con- 

 cerned, however, there is nothing to prevent both of these species 

 being placed here. 



Plaving included some cliaracteristics of this species which, so 

 far I am aware, have not been noted before, it may not be out of 



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