ALTERNARIA FROM CALIFORNIA 
D. G. MILBRAITH 
(WITH TWO FIGURES) 
Frequent occurrence of a distinct spot on the leaves of cabbage 
and cauliflower’ in certain sections of California led to an investiga- 
tion of its causes and distribution. In culture media, infected leaf 
tissue taken from the spot yielded constantly a form of Alternaria 
which was found to be a species hitherto undescribed. Macro- 
scopically the infected area appeared smooth, although somewhat 
sunken, but lacked the profuse growth of conidia and the zonation 
which characterize the lesions produced on leaves of cabbage by 
Alternaria brassicae (Berk.) Sacc. The disease was found to be 
restricted to that district of the state lying directly south of San 
Francisco, where high relative humidity and a uniform temperature 
prevail. In this district there have been planted annually about 
2000 acres of cabbage and cauliflower for shipment to eastern 
markets, and in view of the frequency of the occurrence of the 
disease it may be the cause of a pathological problem in transit as 
well as in the field. 
The first symptom of the disease is the appearance of small 
black specks about 1mm. in diameter. Often countless specks 
appear simultaneously in the laminae. Infection occurs almost 
entirely on apparently vigorous leaves, young as well as old; and 
under conditions of high relative humidity the initial lesion may 
develop into a spot ranging from 0.5 to 1 mm. in diameter in fourteen 
ays. The spots are circular, somewhat sunken, black with a pur- 
plish cast, the center being darker than the margin (fig. 1). The 
color depends largely upon the color of the leaf, for upon pale green 
leaves, as found on Winningstadt and Cannon-ball cabbage, lighter 
spots are produced than on the dark green varieties of cabbage. 
Sporulation of the fungus is sparse on still vigorous leaves, but 
becomes profuse on yellow and detached leaves. 
t The term cauliflower includes both cauliflower and broccoli. 
Botanical Gazette, vol. 74] [320 
