854 



again decreases until at the end of 9 or 10 days, when the growth practically ceases, 

 the liquid becomes clear, and a grayish sediment falls to the bottom of the tube. 



The bacteria also develop well in sterilized juice expressed from the sugar beet, 

 but their developuieut can not be readily watched, as contact with the air causes the 

 juice toturn very dark or eveu black. 



Upon neutral gelatin the bacteria at first form a whitish growth, which becomes 

 pale yellow with age, and the gelatin is eventually li<juefied. Upon acid gelatin the 

 liquefaction proceeds much more slowly. In all cases the gelatin finally becomes alka- 

 line, whether acid or neutral to begin with. 



Up<m agar-agar the growth is about the same as upon acid gelatin, but of course 

 without li((uefaction of the substratum. 



Inoculation with pure cultures into the beet root has been attempted, and results 

 appear to show that the disease was transmitted, but the trials were few, and we 

 desire to repeat tliem before further discussing this part of the subject. * • • 



The present state of our knowledge does not permit us to say how the bacteria 

 gain access to the interior of the beet as it grows naturally in the field. 



Beet scab. — In 18!H the autliors observed seabon beet.sainl found that 

 it was cau.sed by the potato scab tiui<;fus (Oiispura scabits). Thts is iu 

 agreemeut with the iiidepeudeiit observations by H. L. Boliey, M. S., 

 rei)orted in Bulletin Xo. 4 of the North Dakota Station (see Experi- 

 ment Station lieconl, vol. ill, p. Gill): 



The scab has been transmitted directly from the (xitato to the beet by experiments 

 made iu a cool greenliuuse. <Jn February 19, 189"J, a young potato tuber, just removed 

 from a jiut grown jilant and well covered with active seab, was laid in eontaet with 

 ai>erfectly healthy root of a young beet not more than a half inch in diameter. An 

 examination was made 8 days later, but with no distinct evidence of results. On 

 March 'M the beet showed a well-defined seab about a «|uarter «d' an inch across, 

 where the diseased potato touched it, and no trace of scab elsewhere. This result is 

 eo decisive and clear that other te.sts need not be detailed in this connection. 



Pure cultures of the scab fungus ma«le in nutrient solutions show that the organ- 

 ism itself is )»erfectly colorless, but that it exeretes some substance which in the 

 presence of oxygen becomes dark lirown. Cultures have Ix-eu made in the fermenta- 

 tion tubes brought out by Dr. Theobald Smith, which are so constructed that one 

 arm of the tube remains free of all gases. In such a tube the part of the culture in 

 contact with the air becomes a deep brown color and that in the opposite gas-free 

 portion remains unc(di)red for even a month or more, and its final change to br«»wn, 

 if the culture is continued sutliciently lonji. is without doubt due to ditfusion both 

 of the gas absorbed from the air and of the oxidi/ed sultstance, by whieh they )»ai>8 

 from the ojien arm of the tube into the <lose«l arm. 



The scab fungus produces a stronger reactionary eti'ect upon the beet than upon 

 the potato. The scabs of the beet are not tmly of greater areas, but also thicker. 

 The thickness is chiefiy built up of an abnormal growth of delicate cork cells, and 

 may exceed even a quarter of an inch. As a rule it is chielly the surface of this 

 spongy growth that takes on the brown color. • • • 



In a few instances the colored excretion jienetrates to unusual depths, ancl beets 

 are occasionally cut open having several of the ccmcentric annular layers of tissue 

 beneath a scab spot colored a reddish brown. Such disccdorat ions may sometimes 

 extend some inches in all directions. It is supposed that the^e stains are due to some 

 peculiar condition of the root, which permits a greater difi'usion of the excretion of 

 the organism than usual. 



A few instances of a blackish staining of the internal parenchymatcnis tissues of 

 the root have been noted. These ditfer from the la-st chietly in color, iu being cleeper 

 seated as a rule, and iu having no apparent connection with scab spots upon the 



