EXPERIMENTAL PRODUCTION OF PARASITES. 47 



A new series of turnips was then inoculated with the three species of bacteria obtained from the 

 last experiment on plot I. After 24 hours B. fluorescens had attacked the roots from plot I to a depth 

 of 5 mm., and those from plots IV, V, II, and III, in the order named. The other two bacilli attacked 

 the turnips of all plots in the same relative degree but much more feebly. 



A third series of sowings on turnips gave within 24 hours a general attack to a depth of from 

 5 to 8 mm. After 2 days some sections 2 cm. in thickness were traversed through and through. 

 A brownish liquid with fetid odor and alkaline reaction ran out upon the bottom of the crystallizing 

 dish. [This statement relates probably to his B. fluoresccns.} 



After three passages the three bacilli had thus become parasites on turnips, especially those in 

 plots I and IV. B. fluorescens was evidently the most virulent. The other two formed on the sur- 

 face a sort of pellicle, which he says, by cutting off the air, no doubt stopped the progress of the 

 invasion. 



The following experiments were made on carrots. Slices of these roots, taken from the five 

 plots, were sowed with B. fluorescens from a previous culture on carrot, and with the other two 

 species parasitic on the turnips of plot I. After 24 hours carrots from plots I, IV, and V were 

 attacked, the last most feebly. Here again B. fluorescens was the most active. 



The passage of the other two bacilli of the turnip upon the carrot diminished their virulence. 

 But a second series of inoculations, using the products of the attack of each species on the carrots 

 of plot I, gave a general attack on carrots in all the plots. The alteration was deepest on the roots 

 of plots I and IV, and most rapid with B. fluorescens. 



A third passage had communicated to the bacilli a strength of attack such that in 24 hours the 

 carrots were decomposed to a depth of more than 5 mm. Subsequent passages further increased 

 their virulence. That of B. fluorescens was so great that slices 50 mm. in thickness were completely 

 softened in a few days. 



The products of disintegration of the tissues, and the brownish liquid proceeding from them, 

 had a decidedly alkaline reaction. Moreover, the cultures of B. fluorescens gave off a strong odor 

 of ammonia. 



To sum up, the carrots and turnips which were subjected to the influence of excessive appli- 

 cations of nitrogenous fertilizer or of lime showed least resistance to parasitic invasion. On the 

 other hand, the use of phosphoric acid diminished the predisposition to infection. 



These results are said to confirm those of Laurent obtained with B. coli. 



Mature tubers of Jerusalem artichoke and roots of sugar beet appeared naturally immune 

 toward the decay caused by the bacilli studied. 



Jerusalem artichokes from all five plots were inoculated with B. fluorescens, virulent on the 

 carrot. After 4 days the tubers of plot IV only were feebly attacked and a second passage on the 

 same medium did not increase the parasitic aptitude. 



Attempts at inoculation on the sugar beet failed. By inoculation after exposure to 1 per cent 

 soda solution the rot was obtained, but a second transfer to normal roots gave only a slight result, 

 showing that the immunity in this case is very real. 



On account of an accident the potatoes from the experiment field could not be used. Conse- 

 quently fodder varieties cultivated in other fields were employed. 



The pulp of turnips and carrots attacked by the three species of bacillus was used as inoculating 

 material with negative results. An artificial means, invented by Laurent, was then used to 

 diminish the natural immunity. This consisted in immersing the halves of potatoes for 1 hour in a 

 1 per cent solution of soda. Inoculation of these was followed, after 24 hours in the thermostat, by a 

 destruction of the parenchyma to a depth of 3 to 5 mm. At the end of 2 days the attack of B. 

 fluorescens had penetrated to a depth of 15 mm. and that of the other two bacteria to a depth of 8 

 to 10 mm. 



Normal potatoes, cut in two, were then sowed with the three species cultivated on the tubers 

 plunged in soda. Beginning on the next day, B. fluorescens produced a pulp 5 mm. thick. The other 

 two sorts formed a sort of mycoderma as on the turnips and carrots. Subsequent passages on potato 

 increased the virulence of the three species so that even the most resistant tubers were finally 

 attacked. The author considers the parasitic aptitude of B. fluorescens remarkable and thinks this 

 species is undoubtedly a dangerous enemy of many cultivated plants. 



In the pulp formed by B. fluorescens the cells were completely disassociated, but the starch 

 grains remained intact. The pulp infected by the other two bacilli was firm and lumpy, and many 

 of the cells remained in contact. 



The following observations were made on B. fluorescens: 



Inoculated potatoes or turnips examined in March showed plainly that while the pulp was 

 alkaline, the tissue immediately underlying it was acid. In this acid zone no bacteria were present, 

 yet the protoplasm was contracted and the cells were beginning to separate. 



Juice pressed from infected turnips and filtered through a Chamberland bougie was brownish 

 with an alkaline reaction. A part of this liquid was neutralized with dilute hydrochloric acid and 



