WILT OF CUCURBITS. 



289 



carbonate ; also into boiled sterile beet-juice and the same rendered moderately alkaline by 

 various small amounts of sodium carbonate, but in all cases growth was absent, feeble or 

 long delayed. Involution forms were present. 



The result of this series of experiments and of those which preceded it goes to show 

 that the red beet either lacks some nutrient element or contains some substance which, 

 while not destroying the germ, almost completely inhibits growth, and this whether the 

 juice is acid or alkaline or whether sterilized by steam heat or by filtration. The result in 

 tube 5, where after 25 days there was a considerable multiplication, seems to show that this 

 inhibition is due to the presence rather than the absence of some substance. 



The organism is white in the plant and also on a variety of culture-media. It produces 

 no pigment other than the occasional gray stain on potato common to many bacteria. 



In agar and gelatin the best growth along the line of the stab is at the top ; the surface 

 growth above the stab is thin, gray-white, and may eventually cover two-thirds of the 

 surface (fig. 856) or even the whole surface. Fig. 86 shows the appearance of a streak-culture 

 on gelatin. The surface colonies on agar (figs. 87 and 88) and on gelatin are small, circular, 

 slow of growth, gray-white, smooth and usually wet-shining. Internal strias may often be 

 seen by careful manipulation of reflected light (fig. 

 89) . They are not on the surface and can not be 

 seen by transmitted light (fig. 90). Plate-cultures 

 incubated at 25 C. are seldom in good condition 

 for study before the sixth day. Often streak- 

 cultures show a discrete growth either throughout 

 or on the margins (fig. 91). It does not grow on 

 strongly acid gelatin, or on the same after it has 

 been made neutral or feebly alkaline to litmus but 

 is still decidedly acid to phenolphthalein. 



This organism is facultative anaerobic. It 

 will not grow in the closed end of fermentation- 

 tubes in sugar-free, petonized beef-broth, nor in 

 the same fluid with addition of milk-sugar, maltose 

 dextrine (fig. 926), glycerin (Vol. I, fig. 48), etc. 

 When, however, grape-sugar, cane-sugar, fruit- 

 sugar or mannit (?) are added to the beef -broth, 

 the inoculated fluid becomes clouded in the closed 

 end of the tube in the absence of air (see fig. 920 and 

 Vol. I, fig. 47) : No gas is formed in fermentation-tubes or in any of the common media, 

 but inoculated culture-media containing grape-sugar, fruit-sugar, or cane-sugar become 

 acid. This acid is not volatile, but rather is concentrated by boiling, and the writer found 

 that it could be extracted from cultures in bouillon by prolonged shaking with ether. 



In 1909, flask cultures several months old,f set in 700 cc. filtered river water containing 

 35 grams grape-sugar, 14 grams Witte's peptone, and 35 grams calcium carbonate, were 

 submitted to Dr. Carl L. Alsberg for analysis. He did not succeed in identifying the acid, 

 owing to insufficient amount of material, but made the following interesting negative 

 determinations : 



Fig. 85.* 



*FlG. 85. Gelatin stab cultures of Bacillus tracheiphilus after 10 days at 25 C.: o, inoculated June 14; b, June 18, 

 1 904. No liquefaction. Figure a photographed under water, b photographed in air. 



fThe fluid was well clouded after some days and remained so for several months (more than 4). No pellicle formed, 

 only small floating islands which were most abundant near the walls of the flask. There was considerable flocculent 

 precipitate and the fluid became browner than that in an uninoculated flask. The organism at end of 4 months was 

 still pure, living and virulent in flask A, as shown by cultures on agar and on potato, and by inoculations therefrom 

 into cucumber. Eight plants were inoculated by needle-pricks in leaf-blades Nov. 29, and all contracted the disease 

 within 10 days, while 35 check plants remained sound. The flasks B and C presented the same appearance as A, but 

 were not tested until the end of 7 months and 14 months respectively, when the cultures were dead. 



