Vol. 36 



BULLETIN 



No 7 



4 



OF THE . 



-' t 



TORREY BOTANICAL CLUB 



JULY, 1909 



The mildews of the cereals* 



George M. Reep 



In a recent paper^^ I have given a complete summary of the 

 work that has been done on the physiological specialization of 

 the Erysiphaceae. Since that paper was completed Salmon^ has 

 published some results with the hop mildew ^Sjyhaerotheca Humuli 

 (DC.) Burr.]. Salmon obtained ascospores from the hop and 

 sowed them on the same plant, and also on Potentilla reptans and 

 Spiraea Ulniaria, but infection occurred only on the hop. The 

 conidia produced on the hop failed also to infect Spiraea Vlmaria 

 although conidia similarly produced infected the hop. 



Thus far one or more species of frve genera of the Erysiphaceae 

 have been tested with reference to their physiological specializa- 

 tion, namely, Erysiphe^ Microsphaera^ Phyll actinia^ Sphaerotheca^ 

 and Uncimda. As yet n.o species of Podosphaera has been tested. 

 The work with SphaerotJieca^ Microsphaera^ PJiyllactinia^ and Unci- 

 niita has been very Hmited, relatively few tests having been made 

 with species of these genera. Practically all of the work of im- 

 portance has been done with two species of Erysiphe^ vizi, E. 



r 



CicJwr ace arum and E. Gramifiis. 



Although from the morphological standpoint the same species 

 of mildew, Erysiphe Graminis^ attacks all grasses reported as hosts 



+ 



of the mildew, yet physiological differences have been found to 

 exist between the mildews on the various grasses. MarchaP^ 

 first pointed out the existence oi formes speciales in the grass mil- 

 dew. He states that the mildew on each of the cereals (barley, oats, 



* Contributions from the Department of Botany of the University of Missouri 



No. 17. 

 [The Bulletin for June, 1909 (36 : 283-352. pi 20-3^) was issued 17 Je 1909- 1 



353 



