REED: SPECIALIZATION OF PARASITIC FUNGI ohh 
1. Euphorbiae-dulcis s. str. on Euphorbia dulcis. 
2. Euphoriiae-strictae W. Miiller on Euphorbia stricta and E. platy- 
phyllos. 
Melampsora populina Lév. and Melampsora Tremulae Tul. A 
number of different species of Melampsora are recorded as having their 
uredo and teleuto stages on the various kinds of poplars. These rusts, 
however, constitute a group of closely related forms and differ but 
little in their structural characteristics. The main differences appear 
to be in the choice of hosts, especially in the aecidial stage. 
The relationships between the poplar rusts may best be indicated 
by grouping them under the above names. Melampsora populina 
is distinguished from M. Tremulae by the fact that the teleutospores 
are subcuticular while in the case of MW. Tremulae they are subepidermal. 
The uredo and teleuto hosts are also different species of Populus and 
serve further as a means of distinguishing between the two. Klebahn 
(87, 91) has made a special study of these rusts. 
Melampsora populina includes two rusts which can be distinguished 
only by the choice of the aecidial host. These are: 
1. Melampsora Allii-populina Kleb.; aecidial stage on Allium cepa 
and A. ursinum; uredo and teleuto stages on Populus balsamif- 
era and P. nigra. 
2. Melampsora Larici-populina Kleb.; aecidial stage on Larix decidua; 
uredo and teleuto stages on Populus balsamifera and P. nigra. 
Melampsora Tremulae includes four or five rusts whose uredo and 
teleuto stages occur on Populus alba and P. tremula, rarely on other 
species; the aecidial stage is found on widely separated host plants. 
The following belong in this group: 
1. Melampsora Larici-Tremulae Kleb.; aecidial stage on Larix decidua. 
2. Melampsora pinitorqua Rostr.; aecidial stage on Pinus silvestris. 
3. Melampsora Rostrupii Wagner; aecidial stage on Mercurialis 
perennis. 
4. Melampsora Magnusiana Wagner; aecidial stage on Chelidonium 
major. 
5. Melampsora Klebahni Bubak; aecidial stage on Corydalis cava, C. 
digitata, C. fabacea, C. laxa and C. solida. This may not be 
_ distinct from the preceding one. 
Melampsoras of Salix. The Melampsoras on different species of 
Salix constitute a complex group of interrelated rusts. The structural 
differences between the large number of commonly recognized species 
are comparatively insignificant. In order to segregate the different 
species it is necessary to rely, to a large extent, upon differences in 
the choice of host. The willow rusts also afford many parallels among 
the poplar rusts and in some cases it is not possible to distinguish the 
rusts on these two genera except by the choice of host. 
