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 aiirita, S. cinerea, S. caprea, 



S. hippo pha'e folia and S. viminalis. 



b. Larici-daphnoides Kleb. on Salix daphnoides . 



c. Larici-retusae Ed. Fischer on Salix retusa and 6'. herbacea. 



d. Larici-nigricantis Schneider on Salix nigricans, S. glabra and 5. 



hegetschweileri. 



e. Larici- pur pureae Schneider on Salix purpurea. 



f. Larici-reticulatae Schneider on Salix reticulata and 5. hastata. 



Klebahn states that minute structural differences can be observed 

 in a, b, and c. 



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 5. purpurea X S. 



viminalis; to a less extent on 5. daphnoides. 



b. Ribesii-auritae Kleb. on Salix aurita and possibly on S. Caprea 



and 5. cinerea. 



c. Ribesii-grandifoliae Schneider on Salix grandifolia and S. aurita, 



and possibly on 5. arbuscula. 



Klebahn places (a) and (b) under a separate species Melampsora 

 Rib esii- 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 5. 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. 



