4 BACTERIA IN RELATION TO PLANT DISEASES. 



he says "the crops have been almost entirely destroyed by this disease." During the 

 same time the disease made very serious inroads into the cane-fields of the northern parts 

 of the province. He also says that the disease occurs farther south, in the province of 

 Santa Catharina (S. lat. 26 to 28 ), although a part of the injury to cane in that region is 

 ascribed to unfavorable climate, the cold being occasionally too severe in winter (4 C.) 

 and the mean annual temperature too low, i. c, 21.5 C. at Blumenau, whereas cane requires 

 a mean of 24 C. He also seems to think the disease occurs in Cuba, but his only evidence 

 appears to be "much complaint of a sugar disease some years ago." At that time cane 

 was generally reproduced in Brazil by planting the tops of the culms, including the terminal 

 bud. The disease is said to have been most prevalent in a rainy year, and to have caused 

 least complaint in a very dry year. "Repeated investigations at the instigation of the 

 Government have thus far led to no results." 



Inasmuch as the disease had been ascribed to insects by one of the Commissions, 

 Dranert first examined for borers, Coccus sp., etc., but could not in any way connect them 

 causally with the disease. The disease occurred when they were absent and vice versa. 

 On the other hand, as a result of microscopic examinations, he found various minute vege- 

 table organisms in the languishing cane, and to them he ascribed the disease. Accepting 

 Hallier's peculiar view of polymorphism, he believed all these to be various stages of one 

 organism, and experimenting in the same crude way as Hallier, believed he had demon- 

 strated that one grew out of the other. He speaks mostly of an alga as the cause of the 

 disease, but this is only because he believed that to be the terminal stage in the develop- 

 ment of the microscopic organisms (bacteria) seen by him in the yellow gum. These 

 latter were considered to be the spores of the algae, or the reduced forms of the spores. He 

 figures a micrococcus, a cryptococcus (yeast), and one or more fungous or algal (?) bodies 

 as stages of this parasite. Owing to the imperfect technic of the time he was unable to 

 obtain from his cultures results of any value and some of his reasoning is of the post hoc 

 sort. Nevertheless, I believe we may safely accept such of his statements as are based on 

 field observations, and also some of the simpler conclusions he drew from his microscopic 

 examinations. He figures nothing resembling Bacterium vascularum, but his micrococcus 

 is about the right size and it is very easy to understand how he should have mistaken short 

 rods for a coccus, especially with the crude microscope he is likely to have used. There 

 is no doubt whatever in my own mind that the Brazilian cane-disease studied by him was 

 really that subsequently described from Australia by Cobb. He saw the top-rot, the 

 bacterial slime, and the red stain in the bundles. I translate from his short papers in 

 Hallier's Zeitschrift all that is pertinent to the signs of the disease: 



On the contrary, as an infallible sign of the disease there appears in the first place a red stain 

 in the wood and the surrounding cambium tissue of the nodes. As the disease progresses this stain 

 spreads in the same bundles through the whole shaft of the cane, while the parenchyma for a time 

 retains its natural clearness. In the fully developed disease a yellow, thick, fluid substance flows 

 out of the bundles. This substance hardens in the air, but dissolves in water, and under the micro- 

 scope, with very high magnifications, is seen to have only a granular structure. When dissolved in 

 water one can make out very minute cells lying in amorphous heaps, or attached to each other in 

 necklace fashion. 



He goes on to tell how after six to eight days, in the expressed cane-juice, these little 

 cells, which he identifies and figures as a micrococcus, grow out into an alga which produces 

 swarmspores and ferments the cane-juice, with production of hydrogen and carbon dioxide 

 and organic acids. This "alga "he afterwards found in the diseased cane and identified it as 

 the cause of the disease. The yellow masses filling the bundles are regarded as its spores. 



Farther on he mentions the fact that under the influence of this disease the leaves turn 

 yellow and the terminal bud rots. The "spore dust" might enter the plant, he thinks, 

 through insect injuries. 



