26 
WALTER SPURGEON BEACH 
biologic forms, nevertheless there appears to be a degree of specialization 
upon the different species of Helianthus, possibly of a temporary nature 
such as Montemartini (i8) claims for rusts. 
Septoria rubi West. 
Septoria rubi was collected frequently at Urbana upon Ruhiis occidentalis, 
the black raspberry, but was never found upon any species of Rubus be- 
longing to the blackberry, or Eubatus, section of the genus. Since plants 
of the blackberry were often growing in close enough proximity to R. occi- 
dentalis to enable them to become inoculated with the Septoria, it appears 
that the species of blackberry were not susceptible to the fungus on the 
black raspberry. During July thirty leaves each of R. occidentalis and a 
species of blackberry were inoculated with spores of Septoria from the 
former host. Both of these plants inoculated were young, and were growing 
close together in a shaded place. In two weeks all the thirty leaves of 
R. occidentalis were thickly spotted with Septoria, but no trace of infection 
could be found upon the blackberry. 
No definite conclusions can be drawn from the above-described obser- 
vations and the accompanying experiment. The facts may indicate that 
Septoria rubi is split into biologic forms, or that the species of blackberry 
in this locality are permanently resistant to the Septoria. This fungus is 
reported, however, upon twenty-eight or more species of Rubus, distributed 
among all sections of the genus, a fact that makes it appear probable that 
all members of the genus are parasitized. If this be true, the brief data 
above indicate the existence of biologic forms in Septoria rubi. The large 
number of species in the genus Rubus, of which so many are known to be 
hosts of Septoria, makes them an attractive field for a further study of 
biologic specialization. 
Septoria atro-purpurea Peck 
The presence of disease spots without pycnidia is the only indication 
that Septoria atro-purpurea from Aster cordif alius can infect A. ericoides 
and A. laevis. This infection was obtained under prolonged humid con- 
ditions, and it is improbable that it occurs often in nature. These asters 
have not been reported hitherto as hosts for the fungus. This parasite, 
according to specimens in the Herbarium of the United States Department 
of Agriculture, attacks Solidago latifolia and Machaeranthera aspera. The 
data indicate that this Septoria is able to adapt itself to related hosts to a 
considerable degree. 
The disease spots on A. cordif alius are nearly orbicular, with a central 
area of reddish-brown and a margin of light green. In the larger and older 
spots a gray area appears within the reddish-brown. Upon A. ericoides 
the spots were a bright reddish color, w;ith a margin of yellow, and a ragged 
