860 
Journal of Agricultural Research 
Vol. XXXI, No. 9 
epicotyl results in linear lesions occupying deep grooves and in cross 
section it was seen that these lesions extended inward through the 
cambium to the pith and were accompanied by extensive hyper¬ 
plasia of the latter tissue. These lesions result in a break or un¬ 
completed segment in the vascular cylinder, and, as a result of 
enlargement of the rest of the epicotyl tissues, become sharply 
sunken channels or grooves. Shallower lesions were noted which 
had not interrupted or impaired the cambium and which had occa¬ 
sioned a marked hyperplastic response. 
TRANSMISSION OF THE DISEASE THROUGH SEED 
Owing to the abundance of cowpea-pod lesions, many of which 
were found to penetrate through the pod tissues into the seed, actual 
infection of the seed by this organism may occur very readily and 
very generally (pi. 3, C and E). Furthermore, it was found that 
the organism could endure long periods of desiccation on the surface 
of the seed, being found viable after four months of drying. 
In order to determine the possibility of seed transmission of the 
disease, a number of seeds selected from diseased pods collected in 
the fall of 1921 were sown in pots of sterilized soil in the greenhouse 
on March 8, 1922. Among 123 seedlings grown from seeds borne 
directly under pod lesions, 18 showed bacterial spot infection; and 
among 198 seedlings grown from seeds not borne directly under 
lesions, 5 showed infection. These tests proved that the disease was 
carried with the seed and that infected or contaminated seed gave 
rise to diseased seedlings. 
This primary infection consisted of lesions on the hypocotyl, 
epicotyl, cotyledons, and first leaves. In some cases lesions had 
originated at the point of attachment of a cotyledon and extended 
down into the hypocotyl (pi. 3, F) and up into the epicotyl. Infected 
cotyledons tended to remain attached longer than normal ones. In 
one case there was one lesion on each first leaf, each located on the 
under side of the midrib at a point corresponding exactly with the 
location of the other. Considerable local vascular infection and 
localized wilting occurred among these seedlings. The organism 
was successfully isolated from these seedlings. 
Similar tests in pots of sterilized soil were made with 20 lots of 
commercial seed from two sources representing 16 varieties. The 
shriveled, discolored seeds were tested separately. The seed was 
planted April 26, 1922, and the results as noted on May 12 are given 
m Table II. 
The results given in Table II show that the infection was present 
in 15 of the 20 commercial seed lots tested, and occurred in the seed 
from both sources and in seed of normal appearance as well as in 
shriveled or discolored seed. Most of the infected plants represented 
primary seed-borne infection. The organism was isolated from a 
number of the seedlings. The high incidence of infection in some of 
the seed lots, coupled with the large proportion of the lots showing 
infection, indicates the great extent to which the disease may be 
present in cowpea seed. The appearance of a seed can not be 
depended upon to indicate whether or not it may transmit the 
disease: 
