cobb's disease of sugar-cane. 29 



Externally, plant 38 shows much more disease than 37. 



Plant 38 is about 7 feet high and is almost entirely dead as regards leaves. The basal part is 

 devoid of leaves for a distance of 2 feet from the ground and the stem is about 1.5 inches in diameter. 

 The first leaf is partially green, but is beginning to die along the margin. The next leaf is entirely 

 dead. The sheath of this leaf was pricked through when the stem was inoculated. The next two 

 leaves are about half dead, while the next (which is the inoculated one, 38 b) is about three-fourths 

 dead. Two or three of the leaves higher up show traces of green, but the entire terminal bud, com- 

 prising about 1 5 leaves, is entirely dead and dry. All these leaves are rotted at the base, so that the 

 whole mass of them came loose from the stem. 



On removing the leaves from the stem, 10 or 1 1 of the uppermost buds are seen to be well started, 

 some of the upper shoots being 4 inches long. 



Half of the internode into which pricks were made has a water-soaked appearance and there 

 is a large black wound at one end of it. The outside of this internode is sticky to the touch. None 

 of the internodes above this point are healthy. They show water-soaked areas all along one side. 



In the lower foot of this stem there are no red bundles, but above that point one or two red 

 bundles appear. The number of diseased bundles increases from this point up, until at a distance of 

 4 feet from base of stem there are at least 30 diseased bundles. Some are black, others red, while 

 still others are yellow, and after a few minutes standing show a yellow ooze from the cut surface. 

 The upper 1.5 feet of this stem was photographed in toto to show development of shoots (fig. 10). 

 The diseased bundles in the stem are all on one side, which corresponds to the needle pricks in the 

 stem higher up. In the internode next below the pricked one there is a large group of diseased 

 bundles, black, red, and yellow. Yellow ooze shows quite distinctly from about 20 of these. There 

 are at least 100 bundles affected in the inoculated internode. About half of these are black and a few 

 red, but there are a large number which show the yellow bacterial ooze. All of the internodes above 

 this point, 12 in number, are very badly diseased. About one-quarter of the bundles are entirely 

 black in these, and nearly all the others show yellow ooze. There is a small cavity along one side of 

 the stem in three of these internodes, which contains yellow slime. The plates poured from the first 

 internode below the inoculated one miscarried. I did not split the stem longitudinally, as I wished 

 to save it for planting. 



On sectioning: Two cuttings apparently not diseased; four cuttings slightly diseased; five cut- 

 tings badly diseased. 



Plant 37 is about 8 feet high and externally looks to be a very healthy cane. Both inoculated 

 leaves are entirely dead, but with one or two exceptions all the other leaves seem all right except one 

 or two of the upper, which were torn in the ventilator. The basal part of the stem is 1.5 inches in 

 diameter. On cutting the cane, the first red bundle appeared about 2 feet above the base of the 

 stem. In the cut a foot higher there seemed to be no diseased bundles. None showed farther up 

 at all. Cuttings saved for planting: 3 very slightly diseased (1 or 2 bundles red) ; 6 not at all diseased. 



On January 5, 1904, the remainder of these canes were cut out, with the following 

 results: 



27 a and b. Very large cane, no trace of red bundles, nor other signs of disease in either of the 

 nodes into which inoculated leaves ran. 



Another cane, apparently inoculated, is sound. 



J4 a and b. Excellent cane about 10 feet long. A few red bundles run in at. two nodes, which 

 probably bore the inoculated leaves. 



3<? a and b. No evidence of the starting of buds in this or the other canes examined. A large 

 cane, at least 1 o feet tall and 1.25 inches in diameter. No ooze nor red bundles in the internode close 

 below the lower inoculated leaf. In internode above the upper inoculated leaf there are 4 red bundles, 

 from one of which comes a yellow ooze. This was examined under the compound microscope and 

 found to consist of bacteria. In the red bundles of this stem there were comparatively few bacteria, 

 each separate in the field, mostly in pairs and very distinct, the feeble motion probably Brownian. 

 Cover and slide stained. Saved for poured plates. 



36 a and b. Cane about 10 feet. Plain evidence of red staining. In one place 1.5 feet from the 

 ground there are at least 12 red bundles. A little lower down only 1 or 2. One foot farther up there 

 are 7 red bundles and 1 yellowish one. Another foot higher up and immediately under an inoculated 

 leaf are 15 affected bundles; 1 is black, some are red, and some yellow. Apparently an ooze from 

 some. Cutting down from top of stem, about 14 inches above last previous cut, there are about a 

 dozen bundles stained and apparently bacterial ooze from 1 bundle at least. Cut 8 inches lower 

 down, same phenomenon. Slight disease here as compared with that of last year in the Common 

 Green variety. This cane is the most badly-diseased in this lot. Intend to plate out to find if the 



