416 BOTANICAL GAZETTE [NOVEMBER 
caused spotting of the leaves of Sonchus asper. It is quite different, 
in so far as I have been able to discover, from any described species. 
Pure cultures were obtained from spots on Lactuca canadensis, 
produced by means of crude inoculations with fragments of diseased 
leaf tissue of Sonchus asper. Spots were consistently produced on 
Lactuca canadensis by spores of the fungus from pure culture, and were 
not in any essential feature different from those occurring naturally on 
Sonchus asper. The spots enlarged rapidly (2-3 cm. in diameter in 
10 days), the parasitism apparently being vigorous. On cultivated 
lettuce and dandelion small flecks were produced by the spores on plants 
kept under bell jars, but on these hosts the fungus failed to maintain 
itself. This species was the only one under study which failed to grow 
at 30° C., although at 20°C. growth was vigorous. The description 
submitted to me by Dr. J. J. Davis is as follows: 
Alternaria Sonchi Davis, sp. nov.—Spots definite, orbicular to irregu- 
lar, brown to cinereous, usually with a narrow dark margin above, 
darker and immarginate below, o.5-1 cm. in diameter; conidiophores 
hypophyllous, effused, straight or slightly geniculate, cylindrical, obtuse, 
dilute brown, apical portion nearly hyaline, 18-557-8~; conidia 
obclavate with obtuse apex, 5-8-septate, second, third, or first cells, 
one or all, occasionally divided by a vertical or oblique septum, 
80-110 18-20 p, borne singly or in chains of 2 or 3 spores.—JOHN A 
Extiort, Laboratory of Plant Pathology, University of Illinois. 
