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)sestablished 
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 aureum, R. Cynosbati, 
R. gracile, R. prostratum, R. rotundifolium and R. uva-crispa; other 
species not infected are R. floridum, R. oxyacanthoides and R. rubrum. 
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 Rzbes- 
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. Goodenoughu, 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. 
