378 BROOKLYN BOTANIC GARDEN MEMOIRS 
Klebahn (87, 91) and Schneider (133-135) have been the principal 
investigators of the willow rusts from the standpoint of host special- 
ization. While many forms have been segregated out, Klebahn (92) 
has recently indicated the value of grouping these on the basis of 
structural features. The relationship of some of these different willow 
rusts, based upon structural characteristics and physiological special- 
ization, may be indicated. 
Melampsora Larici epitea Kleb. The aecidial stage occurs on 
Larix decidua and the uredo and teleuto stages on various species of 
Salix. Klebahn (87, 91) and Schneider (133-135) have carried out a 
number of inoculation tests and have distinguished the following 
races: 
a. Larici-epitea typica Kleb. on Salix aurita, S. cinerea, S. caprea, 
S. hippophaéfolia and S. viminalis. 
b. Larici-daphnoides Kleb. on Salix daphnoides. 
c. Larici-retusae Ed. Fischer on Salix retusa and S. herbacea. 
d. Larici-nigricantis Schneider on Salix nigricans, S. glabra and S. 
hegetschwetlert. 
e. Larici-purpureae Schneider on Sali purpurea. 
f. Larici-reticulatae Schneider on Salix reticulata and S. hastata. 
Klebahn states that minute structural differences can be observed 
Ine@."O; and: 
Melampsora Ribesii-purpureae Kleb. The aecidial stage occurs 
on species of Ribes and the uredo and teleuto stages on various species 
of Salix. Specialized races occur, according to Klebahn (87, 91) and 
Schneider (133-135), as follows: 
a. Ribesii-purpureae Kleb. on Salix purpurea and S. purpurea X S. 
viminalis; to a less extent on S. daphnoides. 
b. Ribesti-auritae Kleb. on Salix aurita and possibly on S. Caprea 
and S. cinerea. 
c. Ribesii-grandifoliae Schneider on Salix grandifolia and S. aurita, 
and possibly on S. arbuscula. 
Klebahn places (a) and (6) under a separate species Melampsora 
Ribesii-epitea Kleb. 
Melampsora Evonymi-Capraearum Kleb. The aecidial stage 
appears on species of Evonymus and the uredo and teleuto stages on 
various species of Salix. Schneider (133-135) distinguishes two spe- 
cialized races: 
a. Evonymi-capraearum typica Schneider on Salix aurita, S. Caprea, 
and S. cinerea. 
b. Evonymi-incanae Schneider on Salix incana and S. caprea, not on 
S. aurita nor S. cinerea. 
Melampsora Larici-pentandrae Kleb. and M. Salicis-albae Kleb. 
