380 BROOKLYN BOTANIC GARDEN MEMOIRS 



Ochropsora Ariae (Fuck.) Syd., Puccinia graminis Pers., P. 



Caricis (Schum.) Rebent., P. Polygoni-amphibii Pers., Uro- 



myces caryophyllinus (Schrank) Winter, and Uromyces Pisi 



(Pers.) Winter. 

 Certain other rusts might also be looked for in this group as 

 Puccinia coronata (Corda) Kleb., P. lolii Niels. {P. coronifera Kleb.) 

 and P. bromina Eriks. 



2. Heteroecious rusts in which the uredo and teleuto host (or hosts) 



is common to several races which occur on the aecidial hosts: 

 Gymnosporangiiim tremelloides Hartig, Melampsora populina 

 Lev., M. Tremnlae Tul., Puccinia Bistortae (Str.) DC, P. 

 mammillata Schroet., P. sessilis Schneid., P. sihatica Schroet., 

 Uromyces Dactylidis Otth, U. Scirpi (Cast.) Burr. 



3. Heteroecious rusts in which the specialized races are recognized by 



their selection of both aecidial and uredo and teleuto hosts: 

 Puccinia Centanreae- Caricis Tranz., P. coronata Corda, P. 

 dispersa Eriks. and Henn., P. extensicola PIowt., P. glumarum 

 (Schm.) Eriks. and Henn., P. Ribesii- Caricis Kleb., P. Stipina 

 Tranz., Uromyces Poae Rebent. 



4. Autoecious rusts and those whose life history is incompletely 



known. The following belong in this group: Melampsora 

 Euphorbiae (Schub.) Cast., M. Euphorbiae-dulcis Otth, Phrag- 

 midium discifiorum (Tode.) James, Puccinia Absinthii DC, 

 P. biillata (Pers.) Winter., P. Carduorum Jacky, P. Centaur eae 

 Mart., P. Chaerophylli Purt., P. Epilobii-tetragoni (DC) 

 Winter., P. Helianthi Schw., P. Hieracii (Schum.) Mart., 

 P. Leontodontis Jacky, P. Petroselini (DC) Lindr., P. Pulsatillae 

 Kalchbr., P. Ribis DC, Uromyces Fabae (Pers.) de Bary, U. 

 proeminens (DC) Lev. 



Powdery Mildews— Erysiphaceae 



The first work carried on to determine whether a host special- 

 ization occurs among the species of the powdery mildews was that 

 of Neger (107), the results of which were published in 1902. Since 

 then a number of workers have contributed to the evidence for special- 

 ized races in this well-defined group of parasites. In fact, at the pres- 

 ent time, one or more species of five of the six genera of the Ery- 

 siphaceae have been tested. In most cases, however, the data are 

 very meager and it is not possible to draw any definite conclusions. 

 In a few cases, notably for Erysiphe graminis and E. cichoracearum, 

 the facts are better established. 



Erysiphe cichoracearum DC. The host relations of this species 

 was first reported upon by Neger (107) who obtained the following 



