May 13, 1910] 



SCIENCE 



749 



in 1906, and they are in tlie main only verifica- 

 tions or slight extensions of Dr. Appel's state- 

 ments, which I have found to be very trustworthy. 

 It is, however, I believe, the first description in 

 tnglish, and everything has been verified. 



The organism is a non-sporiferous rod, variable 

 in length, usually occurring singly or in pairs, but 

 also forming chains of several individuals; taken 

 from young agar cultures the diameter is about 

 0.6 to 0.8,11, the length 1.5 to 2.5 /i; actively 

 motile by means of peritriohiate fiagella ; stains 

 readily with ordinary stains, but not by Gram's 

 method; rots potatoes (stems and tubers), cu- 

 cumbers, tomatoes, etc. ; aerobe and facultative 

 anaerobe; organism grayisli white on agar and 

 slightly bluish opalescent by transmitted light; 

 surface colonies, on thinly sown + 15 agar, 1 mm. 

 or less in diameter in 48 hours at 20° to 23° C, 

 2 to 3 mm. broad in 4 days; round, smooth, wet- 

 shining, internally reticulated at first, amorphous 

 under 16 mm. and 12 ocular, or with small flocks 

 in the older portion; the buried colonies appear 

 brownish under the microscope, also granular in 

 the center; margin of buried colonies sharply 

 defined; liquefaction of -{- 10 gelatin moderate 

 to rapid; circular white colonies with regular 

 margins on gelatin plates, visible in 18 hours at 

 30° C, in 26 hours at 21° to 23° C; on thin- 

 sown gelatin plates colonies grow rapidly and are 

 frequently 2 centimeters in diameter at end of 

 fourth day at 22° C. ; alkaline reaction in gelatin 

 cultures to which litmus has been added; on 

 sterilized potato slow white to yellowish white 

 growth; characteristic rapid white growth and 

 black stain on raw potato (when streaked from 

 agar) ; grows vigorously and with great rapidity 

 on all neutral and feebly alkaline media; clouds 

 10 c.c. of -f- 15 bouillon in 6 hours at 30° C. and 

 in 24 hours at 13° to 14° C, when inoculated with 

 one 3-mm. loop from a bouillon culture 4 days 

 old at 24° C. ; especially good growth on neu- 

 tralized potato-juice gelatin in which stab-cul- 

 tures rapidly develop a funnel-shaped liquefaction, 

 but less rapid in my hands than in + 10 pepton- 

 ized beef-gelatin; gradual clouding of salted pep- 

 tonized beef-bouillon, and production of chains 

 therein and pellicle on undisturbed old cultures; 

 no indol reaction; tolerates in beef-bouillon a 

 considerable amount of sodium chloride (5 per 

 cent. ) and of sodium hydrate ( + 50 ) ; very active 

 growth in potato-juice with formation of thick 

 pellicle and heavy precipitate; rapid clouding of 

 closed end of fermentation-tubes containing potato- 

 juice, but no production of gas; no growth in 



Cohn's solution; slight greenish tinge in Fermi's 

 solution on long standing; moderate production 

 of hydrogen sulphide; distinct and persistent 

 nitrite reaction in nitrate bouillon but no gas; 

 grows in peptonized beef-bouillon from — 50 to 

 + 16 and beyond, also in potato-broth acidulated 

 to + 46 with citric acid, but no growth when 

 acidulated to +45 with oxalic acid; slow (acid) 

 coagulation of milk with precipitation of the 

 casein; slight reddening and final reduction of 

 litmus in milk; slight production of gas in shake- 

 cultures in some beef-agarg; grows in bouillon 

 over chloroform; in streak-cultures it reddens 

 litmus agar decidedly in 48 hours at 20° C. in 

 presence of either dextrose, saccharose, lactose, 

 gelactose or maltose; it blues plain litmus agar 

 decidedly in 48 hours and does not promptly 

 redden the same with addition of dextrine or 

 glycerine; no reddening of litmus in gelatin- 

 cultures; the acid persists on boiling; produces 

 small quantities of gas from innosit (muscle 

 sugar), lactose and mannit; optimum tempera- 

 ture 28° to 30° C; little growth below 4° to 

 5°C.; minimum temperature for growth in -\- 15 

 beef-bouillon 1° C. or under; ma.ximum tempera- 

 ture for growth in + 15 beef-bouillon about 

 36° C. ; thermal death-point in + 15 beef-bouillon 

 47° C. ; ninety per cent, destroyed by freezing in 

 bouillon. Appel reports loss of virulence in some 

 of his cultures but I have not observed any dur- 

 ing a period of three years. Undoubtedly a very 

 large part of the potato rot of the United States 

 is due to this organism. Bacillus solatiisaprus 

 Harrison is a very closely related, but not iden- 

 tical organism, causing a similar disease in pota- 

 toes. The same may be said of Bacillus atrosep- 

 ticus Van Hall, cultures of which are not now 

 available. The writer has isolated Bacillus phy- 

 tophthorus from potatoes grown in Maine and in 

 Virginia. The following are recommended as 

 quick tests for differential purposes: very thin 

 sowings on gelatin plates; streaks from agar to 

 sterile raw potato; behavior in blue litmus milk; 

 behavior in nitrate bouillon and in Cohn's solu- 

 tion. The right organism should produce big, 

 round, white colonies promptly on thin sown 

 gelatin plates, and should rot potato tubers 

 promptly. It is not always easy to recover this 

 organism from decaying potatoes, since it is 

 quickly followed by various bacterial saprophytes 

 — yellow and white species. The potato disease 

 caused by this organism is known in Germany as 

 " black leg," and by the writer as " basal stem 

 rot." 



