BACTERIA OF PLANT DISEASES. 575 
finally to disappear. The cavities contain innumerable bacteria mingled 
with fragments of the dissolved bundles and of the surrounding parenchyma. 
First described by Dr. J. H. Wakker from the Netherlands, where it 
often causes serious losses in the hyacinth gardens. Not known to occur in 
any other part of the world” (E. F. Smith). 
BACILLUS CAMPESTRIS (Pammel). 
The cause of brown rot in Cruciferous plants. 
_ ‘Pseudomonas canrpestris (Pammel).— Yellow, rod-shaped, motile 
micro-organism. Size and color varying according to substratum, food 
supply, ete. Generally 0.7 to 3.0 by 0.4 to 0.5 # Co.or dull wax yellow or 
canary yellow. Occasionally as bright as light cadmium or as pale as prim- 
rose yellow (Ridgway’s color scale). One polar flagellum. Non-sporiferous, 
so far as known. Pathogenic for various Cruciferous plants, entering and 
dwarfing or destroying the host plant through the vascular system, which 
becomes decidedly brown. Aérobic but, so far as known, not a gas or acid 
producer, 7.e., not facultative anaérobic. Forms cavities around the bundles 
but seems to be only feebly destructive to cellulose. Produces a brown pig- 
ment in the host plant and on steamed Cruciferous substrata, especially the 
turnip. Grows very rapidly on steamed potato cylinders at room tempera- 
tures, but without odor or the formation of any brown pigment. Liquefies 
gelatin. Grows feebly at 7° C., better at 10° C., but still feebly ; grows well 
at 17° to 19° C. ; grows luxuriantly at 21° to 26° C. ; grows very feebly at 37° 
to 38° C. ; will not grow at 40° C.; and is killed by ten minutes’ exposure to 
51°C. Organism closely related to Wakker’s Bacterium hyacinthi, from 
which it differs, so far as I have been able to observe, chiefly in its patho- 
genic properties, its duller yellow color and its higher thermal death point” 
(E. F. Smith). 
PSEUDOMONAS STEWARTI (Smith). 
‘A medium-sized rod rounded at the end and motile by means of one 
polar flagellum, size 0.5 to 0.9 by 1 to 2, no spores observed ; found in enor- 
mous numbers in the vascular bundles of corn (Zea mays) associated with a 
destructive disease of which it is probably the cause; color in the host plant 
and in culture media yellow (buff to chrome or ochre, occasionally a pale, 
dirty yellow) ; aérobic and facultative anaérobic ; grows in all ordinary cul- 
ture media; bears alkali well (soda) and plant acids extremely well; grows 
luxuriantly in Uschinsky’s solution ; growth enormously stimulated by cane 
sugar, grape sugar, and galactose; growth not favored by five-per-cent doses 
of lactose, maltose, dextrin, mannite, or glycerin in nutrient starch jelly ; 
diastatic action feeble, z.e., able to obtain food from starch only with much 
difficulty ; produces alkalies in all sorts of media and acids in the presence of 
grape and cane sugar; reduces litmus slowly; does not liquefy gelatin 
(Stewart); does not liquefy Loffler’s blood serum; grows well at summer 
temperatures of 25° to 30° C. ; does not die out quickly in culture media ; does 
not produce gas; sensitive to light (Stewart); occurs in New York and 
Michigan and may be looked for in all parts of the United States” (EK. F. 
Smith). 
BACILLUS AMYLOVORUS (Burrill). 
Described by Burrill (1880) as the cause of pear blight. Etiologi- 
eal relation to this disease confirmed by Arthur (1884 to 1887) and 
by Waite (1891 to 1895). 
‘Beginning in the spring the germs on the new growth of the season first 
appear on the negative discs of the blossoms. The bacilli live and multiply 
in the nectar and are able to enter the nectar glands without a puncture or 
