8 
The Colorado Experiment Station 
I. Stem Yellow—Typical.—Plate pure; growth just visible after 48 
hours, good after 72 hours; culture picked up 6-19-09. Colony round, 
smooth, grayish white, glistening, slightly raised, margin entire to un¬ 
dulate. Stain: rods, short, moderately thick, rounded ends, many wedge 
shape and curved. 
II. Stem Advanced.—Plate pure; white colony same as “stem yel¬ 
low” above. Growth just visible after 4 8 hours, good after 72 hours. 
Stain: same as “stem yellow.” Culture picked up 6-19-09. 
III. Stem Brown.—Plate pure; white colony same as above; growth 
and stain same; culture picked up 6-19-0 9. 
IV. Stem Green.-.—Plate contained the same white colony, but an 
orange colored colony dominated; this orange colony (1) previously 
shown not to be the cause of the trouble. No cultures picked up. 
V. Stem Yellow No. 2.—Plate mixed; the same white colony domin¬ 
ated; there was also the above mentioned orange colony and a large 
yellow one found once before in earlier plates (2). No cultures picked up. 
VI. Stem Watery.—Plate pure; white colony same as above; growth 
visible after 48 hours, good after 72 hours. Stain: same as “stem yellow” 
above; short, curved rods, wedge shape and irregular. Cultures picked 
up 6-19-09. 
VII. Single Stoma—Old Infection.—Plate pure; white colony and 
stain same as “stem yellow” above. Growth visible after 4 8 hours, good 
after 72 hours. Culture picked up 6-19-0 9. 
(1) Stem tissue—plates of May 27, 1909. 
(2) Stem tissue black—plates of May 2 7, 19 09. 
VIII. Stomata—New Infection.—Plate pure; white colony and stain 
same as “stem yellow” above. Culture picked up 6-19-09. 
IX. Stomata—Black.—Plate pure; white colony and stain same as 
“stem yellow” above. Culture picked up 6-19-09. 
All of the cultures picked up from the dominant white colonies, 
present in all of the plates, have been shown to be one and the same 
organism and when inoculated onto alfalfa plants, all are capable 
of producing the disease. 
Inoculations have been made upon alfalfa plants, grown under 
greenhouse conditions, with the three different cultures which have 
been isolated during this investigation, namely, the characteristic 
white one, the yellow and the orange, and the only one which has 
produced typical symptoms of the disease, in fact the only one which 
has produced any pathological condition whatever, is the dominant 
white colony referred to so frequently above. Cultures obtained 
from stem, leaf, petiole, or exudate, were equally pathogenic. 
Detailed descriptions of this part of the work are given on page 24 
under “Greenhouse Experiments.” 
In order to establish further the fact, that this germ was the 
unmistakable cause of the trouble, an alfalfa plant was inoculated 
June 7, 1909 with our present stock culture of the causal organism, 
to which the name Pseudomonas medicaginis, n. sp. has been given, 
which was isolated from an infected stem May 27, 1909. By June 
19, typical symptoms had developed, and plates were made from 
the yellowish green, watery tissue. On June 21, the Petri dishes 
showed a pure culture of the same white colony and the organism 
