VASCULAR DISEASES OF BANANA. 



171 



tions, reisolations, and reinoculations have been made by him, both on the Moko and on 

 other varieties. Manila hemp plants were also inoculated, but proved quite resistant. 



From a lack of the necessary bacteriological apparatus and supplies but little has been done on 

 the biology of the organism, but it has always been recognized in cultures by the fact that it quickly 

 becomes black when grown on potato cylinders. It is also very short lived and loses its pathogenic 

 power quickly, especially on media which contain 

 starch. In these respects it is similar to Bacillus 

 solanacearum. Inoculations have been made with 

 it several times on solanaceous plants, but so far 

 they have been unsuccessful. The writer is giving 

 the name Bacillus musae to the organism and will 

 at some future time give the complete bacterio- 

 logical chart. 



Although many of the signs of the bac- 

 terial disease are like those exhibited by the 

 Panama disease, they are not the same. 



The two diseases are quite distinct. Though 

 the vascular bundles of plants attacked by the 

 Panama disease are discolored and frequently filled 

 with bacteria, B. musae has never been isolated 

 from such plants. The bacteria in the vessels are 

 usually rapid growing gas formers, and at least, 

 so far as the writer's experience goes, are not 

 pathogenic. The longitudinal splitting of the leaf- 

 sheaths which is a characteristic of the Panama 

 disease [and also of the Cuban disease E. F. S.] 

 is not found in plants attacked by the [bacterial] 

 "moko" disease. Moreover the Gros Michael 

 plant, which is very susceptible to the former dis- 

 ease, seems to be naturally resistant to the latter. 



A species of Fusarium was isolated in Novem- 

 ber, 1909, from a diseased Gros Michael plant and 

 since that time the same fungus has always been 

 found associated with the Panama disease both in 

 Trinidad and in Surinam. Evidence seems to 

 point to the fact that this fungus is the cause of 

 the disease, as was pointed out last year by Dr. 

 Erwin F. Smith. 



The writer received pure cultures of B. 

 musae horn Mr. Rorer and inoculated them by 

 needle-pricks into banana shoots, but unsuc- 

 cessfully. Portions of diseased plants were 

 also received from him, and examined micro- 

 scopically, the vessels being free from fungi 

 and swarming with bacteria. One of the fruit 

 stalks which was green and sound externally 

 extruded from a cross-section numerous small 

 drops of a white bacterial ooze (fig. 76), and 



on making direct inoculations from such drops into petioles, the disease was reproduced on 

 banana in one of the Washington hot-houses (fig. 77), but not on young tomato shoots, into 

 which it was also inoculated. 



The appearance of ten-day-old gelatin stab-cultures of this organism is shown in fig. 78. 

 Fig. 79 shows the manner in which the bacteria sometimes flood out of the vascular bundles 



Fig. 79.* 



*FiG. 79. Longitudinal section through a banana fruit-stalk from Trinidad showing some parenchyma cells 

 occupied by Bacillus musae and others free. 



