504 
Journal of Agricultural Research 
Yot. XXI, No. 7 
a culture of Septoria lycopersici from tomato leaves even when spores are 
used. Moreover, it is still more difficult to isolate Septoria from minute 
pieces of infected tissue, such as may be obtained from spots on tomato 
leaves, because these infected tissues are nearly always invaded by other 
organisms, and a treatment that will kill these accompanying organisms 
will kill Septoria. As Septoria grows very slowly in culture other organ¬ 
isms, if present, soon prevent its development by growing over the sur¬ 
face of the culture medium. It is very likely that Septoria could have 
been isolated from these naturally infected horse nettle leaves about as 
easily as from tomato leaves, however, had not a frost defoliated the 
plants when the plating of the spores was started and made it almost 
impossible to find more spore-bearing material. 
ISOLATION OF ORGANISMS OTHER THAN SEPTORIA FROM' EEAFSPOT OF 
HORSE NETTEE 
While looking for pycnidia of Septoria on naturally infected horse net¬ 
tle leaves, the writers observed a Phoma, an Alternaria, and two species 
of Cladosporium fruiting on the surface of the dead spots. One Clado- 
sporium resembled Cladosporium fulvum Cke. in the shape of its spores 
and in the production of a purple color on both cornmeal and oatmeal 
agar but differed from it in the production of smaller spores. 
The pathogenicity of each of these fungi was tested in four to five 
series of experiments by inoculating with a pure culture thrifty young 
tomato and horse nettle seedlings and keeping them in a moist chamber 
48 to 60 hours after inoculation. No spots resembling those occurring 
naturally on horse nettle or those produced by spraying horse nettle or 
tomato plants with spores of Septoria lycopersici developed on any of 
these plants. Seven out of 100 tomato plants inoculated with the Alter¬ 
naria developed an infection spot, but it was an elongated area following 
the veins and was found also on a few uninoculated plants of the same 
age on the greenhouse benches. Moreover, it did not appear on horse 
nettle. It would therefore seem that the four fungi isolated from horse 
nettle leafspots were merely saprophytes. 
DISCUSSION 
Septoria lycopersici is a very active parasite. It readily infects all 
the varieties of tomatoes grown in the United States and all varieties, 
both wild and cultivated, that the writers have been able to obtain 
through the Office of Seed and Plant Introduction. It infects very 
easily Cyphomandra betacea Sendt., the tree tomato, and a species of 
Solanum from Ecuador, Solanum mammosum h. On this Solanum it also 
produces numerous pycnidia and spores. It is not surprising, there¬ 
fore, that it infects Solanum carolinense. 
Since Septoria lycopersici in pure culture infected horse nettle seed¬ 
lings readily and developed pycnidia and spores both in the greenhouse 
and outdoors, it is apparently able to maintain itself on this host. The 
