REED: SPECIALIZATION OF PARASITIC FUNGI 367 



uredo and teleuto stages on various species of Carex, while the aecidial 

 stage occurs on Taraxacum officinalis, Crepis biennis, Lappa officinalis 

 and three species of Senecio. Schroeter (137) proved that the aecidium 

 on Taraxacum was connected with the rust on Carex brizoides and C. 

 praecox. Later he connected the aecidium on Senecio nemorensis 

 with the rust on Carex brizoides. Dietel (27) connected the aecidium 

 on Lappa with the Carex rust and Juel (72) and Bubak (24) estabhshed 

 the connection between the aecidium on Crepis and the Puccinia on 

 Carex. Wagner (167, 169), however, claims that a particular collec- 

 tion of teleutospores from Carex would not infect Taraxacum, Lappa 

 and Senecio but only one of these aecidial hosts. Some collections of 

 teleutospores infect one aecidial host while other collections infect a 

 still different aecidial host. There is an indication, then, of a special- 

 ization to particular hosts in this rust. 



Puccinia Ribesii-Caricis Kleb. This rust has its aecidial stage on 

 species of Ribes and its uredo and teleuto stages on various species of 

 Carex. Arthur (2, 4, 5, 6, 7, 8, 11, 13, 14), in this country, has carried 

 out inoculation tests with the Ribes-Carex rust for a number of years. 

 He finds that the aecidial hosts include Ribes aureiim, R. Cynosbati, 

 R. gracile, R. prostratum, R. rotundifolium and R. uva-crispa; other 

 species not infected are R. fioridiim, R. oxyacanthoides and R. riibrum. 

 Teleutospores were used from Carex arctata, C. crinita, C. debilis, C. 

 gracillima, C. intumescens, C. pallescens, C. pubescens, C. squarrosa, 

 C. tenuis, and C. tetanica. Fraser (55) reports the successful infection 

 of Ribes oxyacanthoides with teleutospores from Carex arctata and 

 Carex crinita. There appears to be no indication of the existence of 

 specialized races. 



In Europe, Klebahn (87, 91) has extensively studied the Ribes- 

 Carex rust and finds evidence for the existence of five specialized races. 

 The specialization occurs very largely in the choice of the uredo and 

 teleuto host, as all the races pass over to practically the same species 

 of Ribes as aecidial hosts. Klebahn distinguishes the following on the 

 basis of cultural tests: 



1. Puccinia Pringsheimiana Kleb.; uredo and teleuto tages on Carex 



acuta, C. caespitosa, C. Goodenougkii, and C. stricta; aecidial 

 stage on Ribes alpinum, R. aureum, R. Grossularia, R. rubrum 

 and R. sanguineum. 



2. Puccinia Ribesii-Pseudocyperi Kleb.; uredo and teleuto stages on 



Carex pseudocyperus; aecidial stage on Ribes alpinum, R. 

 aureum, R. Grossularia, R. nigrum, R. rubrum and R. san- 

 guineum. 



3. Puccinia Ribis nigri-Paniculatae Kleb.; uredo and teleuto stages on 



Carex paniculata and C. paradoxa; aecidial stage on R. alpinum, 

 R. aureum, R. nigrum, R. rubrum and R. sanguineum. 



