372 
Journal of Agricultural Research voi. xxm. No. 5 
plenty of air, and care was exercised in watering them. Under these 
conditions the disease disappeared entirely by the end of six weeks and 
did not return. 
TECHNICAL DESCRIPTION OF THE ORGANISM 
Bacterium pelargoni, n. sp. 
A motile rod with rounded ends, usually borne in pairs, occurring also in chains 
average size 1.02 by 0.67 n' f one polar flagellum; capsules; no spores or involution 
forms noted; agar colonies cream colored, round, shining, with delicate internal 
markings; liquefies gelatin slowly; reduces litmus and methylene blue and greens 
the latter; produces ammonia, indol (slight) and hydrogen sulphid; does not reduce 
nitrates to nitrites; grows weakly in Uschinsky’s and Fermi’s solutions and not at 
all in Cohn’s; coagulates sterile milk; is aerobic; has feeble diastasic action on potato 
starch; maximum temperature 35 0 C., minimum i°, optimum 27 0 ; thermal death 
point between 51 0 and 51.5 0 ; resists drying six days when 6-day-old cultures are 
used; tolerates sodium hydroxid in peptone-beef infusion to —6 Fuller’s scale 
(colorimetric determination P H 8.7) and hydrochloric acid to +28 (P H 5.7); does 
not produce gas from sugars or alcohols tested; is Gram negative; not acid fast; stains 
readily with earbol fuchsin, methylene blue, and gentian violet; is pathogenic to 
cultivated geraniums, causing dead spots on the leaves. 
The organism is unlike the one described by Lewis from Texas as the cause of a 
spot disease of Erodium amd Pelargonium and may be called Bacterium pelargoni. 
It has been reported from various parts of the Eastern United States from Virginia 
to Massachusetts and has been under observation in the Laboratory of Plant Pathology, 
Bureau of Plant Industry, United States Department of Agriculture, at different 
times for the last 20 years. 
SUMMARY 
A bacterial leafspot disease of the cultivated geranium occurs wide¬ 
spread in the Eastern States. It is mostly a greenhouse disease but 
occurs occasionally on plants grown out of doors. 
The organism was isolated from diseased plants received from different 
sources and the disease reproduced on the leaves of healthy plants. 
Warm, moist conditions with poor ventilation are necessary for the 
organism to infect the leaves extensively. 
Care in regulating the temperature, air, and moisture conditions of 
the greenhouse and in giving plenty of space to plants grown out of doors 
will go far toward preventing the appearance of the disease and toward 
curing it when it is present. All spotted leaves should be removed and 
destroyed. Very sensitive varieties should be discarded. 
The name Bacterium pelargoni is suggested for the organism causing 
the disease. 
