732 BULLETIN 727, U. 8S. DEPARTMENT OF AGRICULTURE. - 
ton (14) finds the summer heat of Louisiana inhibiting bean anthrac- 
nose, and a similar situation may have existed in the case under 
consideration. 
Very heavy rainfall on August 3, 4, and 5 was followed by a marked 
spread of the disease in fields 1 and 2. A rather careful inspection 
of field 1 on August 15 disclosed about 26 more or less distinct addi- 
tional centers of infection, accompanied by rather widely scattered 
secondary infection in many cases. A similar situation obtained in 
field 2, and careful inspections on August 11 and 14 yielded a total 
of about 30 centers of infection, around most of which there was 
extensive secondary infection. This tended to extend farthest in 
the direction of the slope of the land and will be referred to later 
in connection with the consideration of water dissemination. On 
August 17 the disease was generally distributed in field 3 among the 
plants which had not been removed, especially at the lower corner 
of the field. A small private patch adjacent to this corner and hith- 
erto undiseased, which received much of the drainage from field 3, 
also showed much infection of uniform age about this time. In field 
4, occupying a very gentle slope, the disease did not become preva- 
lent. By August 18 there were 10 centers in field 5 from which con- 
siderable spread had occurred, notably in the direction of the slope. 
Since an incubation period of a week or more is quite normal in the 
field, this first general spread of the disease seems to be closely asso- 
ciated with the period of abundant rainfall above mentioned. 
During the week after August 18 the destructive effect of the 
disease became very apparent; the centers of infection were character- 
ized by the death of the older diseased leaves and the rapid blighting of 
those near by. New centers of infection were found among the plant- 
ings of cucurbit varieties. Somenew infection, due perhaps to the light 
rain of August 10, also appeared, but nowhere in such abundance as 
the infection which followed the heavy showers of the first of the 
month. Here it should be noted that, following this rain, the daily 
mean temperatures were quite low for five days. Occasional incipient 
lesions appearing within the infected areas previous to the rain of 
August 26 indicate that rain is not essential to infection. An hypoth- 
esis to account for the latter phenomenon is that, while rain is essen- 
tial to the actual dissemination of the spores, germination and infec- 
tion may occur later in the heavy dew which is formed during clear 
nights in August. 
No anthracnose appeared in field 19, occupying level muck soil, 
until August 24, and it then remained confined to two small centers. 
In fields 9 and 10, belonging to private growers, no anthracnose 
appeared during this season. 
Observations of August 21 to 31 made upon fields 1 and 2 showed 
that, as a rule, no marked extension of the areas of infection had 
