856 
Journal of Agricultural Research 
Vol. XXXI, No. 9 
slants. No growth was obtained from smears that had been dry 40 
minutes, and in most instances no growth was obtained from smears 
that had just dried. 
To test the resistance of the organism to drying on cowpea seeds, 
small quantities of seed were placed in Petri plates, moistened, steril¬ 
ized in the autoclave, and allowed to become air-dry. A water sus¬ 
pension of the organisms was then poured over this sterilized seed 
and allowed to dry. The seed was tested at intervals by planting 
in agar-poured plates and the organisms were found alive during the 
following four months. Furthermore, it has been found that the 
organism lives over winter in the seed, so that it is evident that it 
is highly resistant to drying on and in cowpea seeds. 
Tisdale and Williamson (24 f V • found the organism alive in 
lima-bean leaves dried 2% years. In the writers’ experience the 
organism has not generally been found viable in the older tan-cen¬ 
tered leaf lesions on cowpeas; it has a tendency to be rather 
short lived on potato-agar slants, much more short lived than certain 
yellow organisms such as Bacterium phaseoli E. F. S. and Bact. 
vesicatorium Doidge. 
TAXONOMY 
The organism causing bacterial spot of cowpea is not identical 
with any of the previously described bacterial parasites of cowpea, 
being clearly differentiated in its chromogenesis and other salient 
characters. It was briefly described in March, 1923, ( 6 ), and given 
the name Bacterium vignae n. sp. Upon the appearance of this 
preliminary note the writers received a letter from W. B. Tisdale 
calling attention to the marked similarity of this organism to the 
causal organism of the lima-bean disease, a description of which was 
in press at that time and appeared four months later (24)* The 
causal organism of the latter disease was designated Bacterium 
viridifaciens n. sp. 
The lima-bean disease was found rather commonly in gardens 
about La Fayette, Ind. The causal organism was isolated from 
pod lesions and proved to resemble closely the cowpea organism. 
With the organism isolated from lima beans, abundant and typical 
infection of cowpea seedlings grown under a cloth cage in the field 
was obtained August 15, 1923, along with infection of lima-bean seed¬ 
lings. In another cage, typical infection of lima-bean seedlings was 
obtained with one of the strains isolated from cowpeas. Later a 
culture of Tisdale’s organism was obtained from the University of 
Wisconsin, and with it successful inoculations of cowpea seedlings 
with the production of characteristic bacterial spot lesions were 
obtained in the greenhouse in April, 1924. These cross inoculations 
indicated beyond doubt the identity of the two organisms. 
In the meantime, however, the cowpea strain, the strain isolated 
from lima beans at La Fayette, Ind., and the original lima-bean strain 
from the Wisconsin laboratory were carefully compared as to a large 
number of cultural and physiological characters and found practi¬ 
cally identical. These tests included the ordinary media such 
as gelatin, agars, and milk with indicators, agar and bouillon with 
the six carbon sources and the three hydrogen-ion indicators pre¬ 
viously mentioned, toleration of sodium chloride, toleration of 
acidity, blood media, and Cohn’s, Fermi’s, and Uschinsky’s media. 
Furthermore, the published description of Bacterium viridifaciens 
