


1901] BRIEFER ARTICLES 273 
all other uniflagellate organisms studied. Organism prefers neutral or 
acid reaction of culture medium, a moderate degree of alkalinity 
inhibiting growth; it liquefies neutral and acid gelatin. Produces no 
gas in fermentation tubes of sugar solutions; growth confined to neck 
and bulb of tube, hence aerobic, no growth under mica plate. Colo- 
nies in malic acid potato gelatin and agar circular; at first clear but 
soon decidedly yellow, margin sharp. This organism is distinguished 
from P. campestris, the most nearly related species of the genus, aside 
from the characters already assigned, in producing an abundant and 
bright yellow pigment on the surface of extracts of the leaves of the 
following plants, while P. campestris produces little or no pigment 
upon such extracts: walnut (/uglans regia), magnolia (Magnolia macro- 
phyla), fig (Ficus Carica), castor bean (Ricinus communis), loquat 
(Eriobotrya Japonica). 
Organism strikingly pathogenic to nuts, leaves, and tender branches 
of Juglans regia. In the young walnuts the epicarp and forming shell 
and kernel are destroyed, in the older nuts the epicarp alone may be 
affected. The leaves are commonly attacked along the veins and on 
the petiole, the organism often entering the vessels. The branches 
become infected near the growing point, and all tissue systems are 
destroyed, the organism entering and wintering in the pith cavity; it 
also winters in fallen nuts. An unlimited number of infections may 
be induced— and thousands have been so induced —by spraying the 
young nuts with a pure water culture of the organism. This test shows 
the germ to be one of the most active, self-effective parasitic or patho- 
genic species of the genus yet known to infect plants. 
Pseudomonas campestris has not been found infesting the cabbage 
fields of the regions where the present disease prevails. Walnut bac- 
teriosis is known to exist over large areas in southern California and 
to a limited extent in the central and northern portions of the state.— 
NEwrton B. Pierce, U. S. Dept. Agric., Div. Veg. Phys. and Path., 
Pacific Coast Laboratory, Santa Ana, Cal. 
