THE HUMID GANGRENE OR POLVILLO. 87 



It is evident that Spegazzini selected this particular schizomycete because under certain 

 cultural conditions it was able to produce a red pigment. To this conclusion I think he was 

 led by the red color visible in the affected canes, and thus probably overlooked the real cause 

 of the disease, i. e., the yellow slime. 



He obtained a good growth of the fungus, and some growth of the bacillus with a violet 

 color, on sugar, boiled starch, and lemon-juice. Both the bacillus and the fungus grew well 

 on nutrient gelatin and also on nutrient gelatin with boiled starch or with sugar, or when 

 both together were added to the gelatin. The best growth of both was on gelatin containing 

 boiled starch, sugar, and lemon-juice. On this medium there was excellent growth and a 

 magnificent red color, together with the production of a strong odor. No growth could be 

 obtained on gelatin, boiled starch, sugar, and water of ashes. He also obtained growth on 

 scrapings from the hearts of sugar-cane, on onions, and on potatoes, but always in acid media. 

 The best temperature for the bacillus is said to be 34 C. The red pigment was produced 

 only by the bacillus, and only in the presence of air. This organism is said to liquefy gelatin, 

 forming a beautiful red color on its surface. "All neutralizing or alkaline substances stop 

 growth immediately, as also all the common antiseptics." The bacterial organism occurs 

 in the form of septate filaments of considerable length. These soon separate into segments 

 i .5 to 3/n in length by 0.5 to 0.8/1 in diameter, cylindrical, truncate at the ends. When they 

 are old they are said to produce two to four small globules in their interior, and these are sup- 

 posed to be spores, 0.5 to o.j/j. in diameter, the membranes becoming dissolved, and the 

 spores adhering together for some time in the form of chains resembling micrococci. The 

 bacillus is said to resemble closely in its morphological, biological, and microchemical char- 

 acters Bacillus sorghi* 



Inoculation experiments undertaken in the cane fields did not succeed. Nine cane 

 plants were inoculated by scarifying the stems and applying juice obtained from the rotted 

 tops of diseased canes. None of these plants developed the disease. Spegazzini also took 

 some of the thick, gummy material from the inner face of the leaf-sheaths, and diluting it 

 with a little water, spread it on the upper side of the higher leaves of various healthy canes. 

 This gum he states appeared under the microscope to be composed almost entirely of micro- 

 cocci or germs of bacteria. The experiment failed. "I attribute this to heavy rains which 

 occurred at this time. " On his return to La Plata he made additional inoculations in the 

 Botanic Garden, which he states were successful. 



I again tried the same system, employing the same mucus and cultures which I mixed with sev- 

 eral times their volume of dissolved gum arabic; but in order to avoid the injurious effects of the rains 

 I put the solution on the leaf-sheaths themselves, and as a further precaution I covered with a canvas 

 the plants which had been inoculated. The result this time was wholly satisfactory ; at the end of 5 

 days there appeared on the interior side of the leaf-sheaths some orange-colored dots, which later 

 became red, and some days afterward there appeared the stain (spot) which extended to the leaves, 

 involving all of the ligular border and lengthening towards the upper part of the lamina. Moreover, 

 out of six cane plants so treated, in two began total decomposition of the tops (cogollos), giving off 

 also the repugnant and characteristic odor; at the same time there appeared at the base of these two 

 plants many buds or side branches, as occurs in the cane plantations affected by Polvillo. 



Spegazzini believes that planters are themselves largely responsible for the spread of this 

 disease. I quote as follows: 



Stocks, and especially seed-canes which are diseased must necessarily produce diseased canes, or 

 at least those which tend in this direction. The extraordinary increase of the disease which has been 

 observed in the cane plantations during the last two or three years corresponds exactly to the culmin- 



*In 1896 Spegazzini made the following additional statement: "Bajoel puntode vista taxonomico estaespccie 

 seria muy cercana al Bacillus marcescens (Bizio) Trev. (el milagroso Mierococcus prodigiosus Cohn, de los autores), pero 

 se distingue dc el facilmente por las extremidades tronchadas de sus articulos y por la sustancia roja que segrcga, la 

 cual no altera su tinte ni por los acidos ni por los alcalinos. " 



