ANTHRACNOSE OF CUCURBITS. A5 
melons unquestionably is another means of long-distance spread of 
the disease provided infectious material reaches the fields. 
It seems fairly safe, however, to eliminate all of the above factors 
except overwintering as rather remote possibilities. As an explana- 
tion of the appearance of the disease in new localities, all evidence 
points toward introduction with the seed. Previous workers have 
suggested this possibility, notably Sheldon (46; p. 127-137), Garman 
22, p. 51), Eckardt (11), and Eriksson (16, p. 126-127). Eriksson 
presents observational evidence which strongly indicates the intro- 
duction of anthracnose into greenhouses in Sweden with cucumber 
seed from England. 
FIELD OBSERVATIONS. 
The experimental field at Princeton in 1915 had previously been 
in sod for seven years. Anthracnose appeared in this field as soon 
as in any other fields of the region. So far as could be learned none 
of the five experimental fields at Madison in 1916 had previously 
grown, host crops, yet the disease appeared simultaneously in all 
of these fields and in practically no other fields or gardens of the 
surrounding territory. In the watermelon industry of the South 
crop rotation is necessitated by the ravages of the wilt, yet anthrac- 
nose recurs annually. 
Instances could be multiplied, but sufficient evidence has been 
adduced to show that the disease appears quite commonly in new 
fields. In a’case such as that presented by the 1916 Madison fields 
there seems to be but one plausible explanation, namely, disease 
introduction with the seed. 
The very manner in which the disease originated in these fields 
suggests this hypothesis. The disease first appeared in the Prince- 
ton field and in the Madison fields in what we have termed ‘original 
centers.’”’ These were scattered here and there through a field and 
were usually limited to a comparatively small number per acre 
(figs. 13 and 14). With a disease as infectious as this it is not 
always easy to differentiate between original and secondary centers, 
but in fields under constant observation those centers appearing 
first and about simultaneously: may safely be termed “ original.” 
The nature of these initial infections furnishes another argument 
in favor of their origin in situ. The first original center found in the 
Princeton field consisted of two adjacent plants not yet large enough 
to ‘‘run.”” These plants bore lesions on the first and second foliage 
leaves. Since the rows had already been thinned, several plants had 
been removed, between and adjacent to the two above noted, and 
the hypothetical originally diseased plant might already have been 
removed. 
In 1916 the first center of anthracnose found in field 1 consisted 
of two adjacent plants, one bearing one lesion on the fourth leaf, the 
