7 
A Bacterial Disease oe Alealea 
abundant. In other words, pure cultures were obtained in 62 per 
cent of the original isolations and in 81 per cent this white colony 
was dominant. In two out of twenty-six isolations or in seven per 
cent, it was absent. Plates made from the moist or freshly dried 
exudate, as a rule, gave pure cultures of the same organism. 
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. 
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 
was reisolated on an agar slant. When compared with the original 
culture, the recovered organism was identical both in the hanging 
drop and when stained with aqueous fuchsin. The reisolated culture 
was again inoculated, June 25, by needle pricks into three different 
stems, and all of the inoculations gave positive results; the needle 
pricks showed a yellow, watery zone around the point of infection 
after nine days, and later turned black. When material from these 
diseased areas was examined microscopically, August 16, the same 
milky cloud appeared in the mount as has been described for field 
material, and swarms of motile rods were visible. 
In all, one hundred and two inoculations have been made with 
this culture, introduced either by scraping the stem or by needle 
pricks, and positive results have been secured with one hundred per 
cent of the infections. Control inoculations with a sterile needle 
have been carried along with all of the experiments, and in no case 
have any of the check plants developed symptoms of the disease. 
method oe infection. 
In an effort to secure a satisfactory explanation of the method 
of infection, the writer spent over a month in the field where the 
disease is most prevalent. As a result of the daily observa¬ 
tions and the gross and microscopic examination of more 
than three hundred plants, collected at all stages of the disease, be¬ 
fore it made its appearance and until it was flourishing, he believes 
