COBB'S DISEASE OF SUGAR-CANE. 



white or pale stripes appeared as secondary signs in the uninoculated leaves of the same 

 shoot and in young shoots from stools bearing inoculated diseased canes. Etiolation has 

 been less marked in the other varieties tested, but they have in every case been more 

 resistant to the disease. 



All of these conclusions are based upon pure-culture inoculations made in Washington 

 hot-houses, the writer never having seen the disease in the field. 



Since premature development of the male in- 

 florescence is one of the striking signs in sweet maize 

 attacked by Bacterium steu'arti, and since an incli- 

 nation to bloom is also a conspicuous feature of 

 sugar-cane attacked by Sereh, the writer has been 

 at some pains to learn whether it occurs in Cobb's 

 disease. Cobb does not mention it, neither does 

 Tryon himself, but in Tryon's paper "arrowing" 



is mentioned by several 

 planters as one of the gen- 

 eral signs of deterioration in 

 the widely planted Rappoe 

 or Rose Bamboo cane, and 

 these men were planters in 

 just those districts of Queens- 

 land where the "gum dis- 

 ease" prevails extensively. 

 I quote from them as follows 

 respecting this variety, 

 which, at that time, was the 

 common cane of Queensland : 



Moreover, the plant was 

 tending to become shorter lived, 

 a feature that appeared to be 

 evinced by its frequent arrow- 

 ing. Arrowing seemed to be 

 the last event in the life of the 

 plant an indication that it had 

 arrived at its term of life. For- 

 merly an "arrow" was quite a 

 curiosity, especially in the case 

 of cane grown upon rich scrub 

 soil. In fact it might be said 

 that Rappoe generally did not 

 arrow. Now it arrowed com- 

 monly. (E. Young, of Fairy- 

 mead.) 



Until three seasons ago he 

 scarcely remembered to have 

 ever seen an arrow ; now, if the 

 plants were mature, nearly the 

 whole plantation arrowed. 

 (H. O. Nott, of Windemere.) 

 f* "* F* ' 2 -t For some years past the 



cane has arrowed to a larger extent, especially in the sandy flats, and much more so than in for- 

 mer years. (Mr. McGuigan, Island Plantation, Mary River.) 



*FlG. ii. Longitudinal section through basal part of inoculated sugar-cane 8 or 12, showing red nodes (dark 

 cross-stripes) and buds pushing at X, X. X, X. Photographed about May 6, 1903. '. e., 3 months from date of inoculation. 



tFlG. 11. Longitudinal section through a mottled (red and yellow) bundle from the stem of a sugar-cane inocu- 

 lated with Bact. vascularum. showing how the bacteria fade out above into an amorphous red mass. Slide 310 (17. 

 For a detail see fig. 26. 



