i 



COBB'S DISEASE OF SUGAR-CANE. 45 



getting worse and worse. In the third one down there are 30 or 40 stained bundles. The surface of 

 this internode looks perfectly sound. The next node below contains fewer stained bundles ; the next 

 one down is very bad, mostly in the middle; the next one below that is also very badly stained; the 

 next one below that shows less stain; the next one below that is free from stain, except one or two 

 bundles. The next one (about a foot from the ground) shows no stain. From this point down the 

 cane seems to be perfectly sound. Examined these red vessels under the hand-lens; result: no dis- 

 tinct bacterial ooze, except possibly in one place, and it will take the compound microscope to settle 

 this. 



A large old cane, 2 inches in diameter at the base. Basal buds well developed. Stem naked up 

 to about 6 feet. Cross-section at the top of stem sound ; continues sound for many feet. The cane is 

 so soft on cutting that I believe it grew since the date of inoculation. It is sound throughout. 



Old cane. Bears label 766. Basal buds well developed. Cross-section at base sound. Leafy 

 only in the upper part. Leaves are not white-striped. Stem sound on cross-section for many feet. 

 First signs of red stain in the middle of the stem at a level of about 3 feet; slight in the next internode, 

 and in the next two. It seems to run out in the next one about a foot from the ground. From here 

 downward the stem shows no signs of disease, except a bright 

 red bundle in one of the basal internodes. Examined under 

 the hand-lens. No evidence of bacterial ooze. Staining 

 comparatively slight in this plant. 



I have left all of the numerous young shoots, they 

 look so healthy. 



General Remark. There is more red stain in 

 these stems than any other lot thus far examined, 

 but whether it means that there is a slight bacterial 

 infection or only that the stems are very old and going 

 naturally over into a condition preceding decay is 

 what I do not know. The general appearance of the 

 pale reddened bundles is non-typical for Cobb's dis- 

 ease as I have seen it in other varieties. Examined 



the suspected stems microscopically, and was not "' ~ ' 



definitely certain of bacteria in any of them. 



On February 9, 1906, the examination of canes inoculated in house No. 4, May 22, 

 1905, was continued as follows: 



Striped Green. 



North (inoculated) row: 



Several old canes. Well developed ripe buds ; large. No external signs in canes either at top or 

 bottom. The canes were now cut open (every internode). One cane showed traces of red and 

 yellow bundles in the basal part : Confined to a few bundles in a few nodes and internodes. Signs so 

 slight that only the use of the microscope will settle it. Doubtful under microscope ; seem to be some 

 bacteria. Johnston thought them bacteria. The young healthy shoots not cut out. 



CrytUlina. 

 North (inoculated) row: 



Sixteen large canes, most of them fully mature. Young healthy shoots not cut out. All canes 

 large and sound looking. Free on cross-section at top and bottom from any signs of gum disease. A 

 very few red bundles in one cane a node near the base. One cane (less mature than the other) 

 shows distinct red and yellow bundles (a few) in some of the basal nodes and internodes, and what 

 looks like bacterial slime is oozing from some of the bundles, yellow slime from some and red slime 

 from others. Will examine microscopically. Three other canes show a trace of red and yellow 

 bundles in one or two basal nodes (very slight, hardly to be called diseased). 



LABORATORY NOTE. Under the microscope the one most affected showed great quantities of 

 bacteria (short rods, single or paired) in the yellow ooze, and also in the red ooze. Stained and 

 mounted the latter (fig. 18). Mr. Johnston has made plates from this stem. 



*Fic. 1 8. Contents of red slime from a vascular bundle in the interior of the stem of a sugar-cane (variety Crys- 

 talina) 9 months after inoculations with Bad. tascularum. Surface of stem sound. Slide ss, Feb. 9, 1906. Stained 

 with carbol fuchsin. Drawn with a Zeiss 3 mm. 1.40 n. a. oil-immersion objective. No. 12 compensating ocular, and 

 Abbe camera. 



