42 BACTERIA IN RELATION TO PLANT DISEASES. 
beer. The mould did not develop, but on a slice of carrot from plot IV, there appeared a little 
bacterial colony of a ropy consistency, made up of short bacilli, introduced probably when the conidia 
were sowed. All his attention was then focussed on this bacillus. 
Inoculations were made with a flamed scalpel on slices of carrot kept at laboratory tempera- 
ture. Sections from plots II and IV became infected in 4 days while those from I and III remained 
uninjured. ‘Two later attempts to inoculate I and III failed. 
Tnoculations of slices of carrots from all plots, using the microbe obtained from IV of the preced- 
ing series, gave positive results. Another series using material from plot II of the second series 
gave a general development on roots from plots I, II and IV, but scarcely any colonies on those 
from III. ~ 
A fourth series, however, inoculated with bacteria taken from slices of plot I (third series, kept 
at a temperature of 25° C.) gave a growth on all the slices from all the plots. 
Thus the microbe had become parasitic even upon the most resistant carrots after three pas- 
sages through less resistant ones. 
Results absolutely comparable were obtained with tubers of potatoes: Thus, tubers from plot 
IV were readily attacked, those from plots I and III less so, while those from plot II were success- 
fully inoculated only after four passages of the bacillus through tubers from plot IV. 
When the microbe grew it finally transformed the invaded tissues into a pulp, composed of 
disassociated cells in which the starch-grains persisted. The cylindrical bacilli swarmed around 
and finally within the cells. 
This schizomycete was identified as B. fluorescens putidus. It was readily cultivated in a 
mineral solution: 
Neutraliatimonitum phosphates cc ccy- sot sierst he ais crcnectvie aia uatarees, sianehetsl casero wl sieyee oie rai a 
Neutral! potassium: phosphates: acc. oc aes ieits ae sicistol aati einicie tsie Biatavos ore alate ns eiatoueisiane 
DWiateltiels oh rcr cine sireetsimitata yee erin fre. ateletcparens eve sas s\oin aisle: dima Sei wie, eure Gye aleepn ere Less 1,000, 
2 
2 
IMs PTIESIUEAI SULDHATC§.< devercaecrts onal her Aclorn ls Soci ene. oe moots! cnnlesevah tote lenguaue seucnalieta7s ere ate ies nds I 
to which had been added various organic matters—sugars; alcohols; peptone; asparagin; succinate, 
lactate, citrate and tartrate of potassium, etc.—but in such cultures it lost its virulence, to such an 
extent that inoculations on tubers from plot IV gave negative results. Only by diminishing the 
resistance of the potato cells by the use of alkaline solutions was infection made possible. 
In March, a new series of experiments was begun, the four plots receiving fertilizers per hectare 
as follows: 
Plot I. 500 kg. sodium nitrate and 800 kg. sulphate of ammonia. 
Plot II. 2,000 kg. kainite, containing 13 per cent of potash. 
Plot III. 2,000 kg. superphosphate of lime, containing 15 per cent of phosphoric acid. 
Plot IV. 40,000 kg. quick lime. 
A fifth plot received 2,750 kg. sodium chloride per hectare. This was to determine what effects 
might be attributed to the osmotic action of large quantities of soluble salts. In a sixth plot the 
plants mentioned below were cultivated without special fertilizers: Eight varieties of potatoes 
were used, namely three which had the reputation of being subject to disease, viz., Marjolin, Early 
Rose, and Blanchard; three considered to be resistant, viz., Chave, Simson and Chardon; and two 
other sorts, viz., Pousse Debout and Zeland. ‘The tubers of Simson used as seed were harvested 
from the corresponding plots of the previous year. In addition to potatoes, Nantes carrot, Witloof 
chicory, Jerusalem artichoke and a local variety of sugar beet were cultivated on these plots. 
All the seed-tubers sprouted and developed regularly, but in plot V the salt plainly injured the 
germination of seeds. 
At the time for inoculation, the fluorescent bacillus was found to be lacking in virulence as it 
had been kept on artificial media. ‘Therefore, Laurent undertook to get the bacillus as in the 
first place, but obtained this time a motile nonfluorescent organism (2 to 5 X 0.5 to 0.6 /4) the 
colonies of which it is said resembled those of Bacillus coli. Submerged colonies were little yellowish 
disks, while surface ones were pearly white, spreading, with a circular or sinuous border. 
The different varieties of potatoes yielded very differently in the several plots, showing that 
each variety has its own requirements as regards mineral foods. 
Halves of tubers of Marjolin from all the plots were inoculated with the bacillus from tubers 
of plot IV, and kept in the thermostat at 30°. All were attacked within6 hours, but while penetra- 
tion continued in sections from plot IV, reaching 10 to 12 mm. by the fourth day, it ceased in all 
the others by the second day, with a healing of the spots. 
Slices of Early Rose from all plots, inoculated with cultures from tubers of plot IV in the pre- 
ceding experiment and kept at 30°, offered little resistance to the disease, except in tubers from plot 
V where the sticky surface layer reached a thickness of 4 to 5 mm. 
