COBB'S DISEASE OF SUGAR-CANE. 31 



SERIES V. 1904. 

 The fourth set of inoculations was made June 22, 1904, on canes planted in December, 



1903 



All inoculations were by needle-pricks through the leaf-sheaths into the stem. The 

 cultures used were strains plated out of plants Nos. 7, 9, and 1 1 , inoculated February 6, 

 1903. Only cultures from plant No. 7 gave positive results, and it is probable that the two 

 subcultures from plant No. 9 and the one from plant No. 1 1 were made from non-infectious 

 yellow colonies resembling Bacterium vascularum on agar, but not identical. It was thought 

 at the time of inoculation that these might be different, as they browned the agar in a way 

 the true organism does not. The plants inoculated from these suspected tubes have 

 starred numbers. 



In making the inoculations the surface bloom and the prickles were first rubbed off the 

 lower part of the selected leaf-sheath ; the surface was then rubbed with a few loops of the 

 yellow organism scraped from the slant agar, and eight or ten needle-pricks were made 

 through the sheaths into the center of the stem. Check-pricks were made on each variety. 

 These are the inoculations referred to at the end of my German paper. 



On September 27, 1904, the condition of the sugar-cane inoculated June 22, 1904, was 

 as follows: 



Striped Green, f 



No. jp*. A large-sized cane, 8 feet long and 1.5 inches in diameter. The inoculated internode 

 is about 2 feet from the base of the cane. No signs of infection in the internodes directly above or 

 below the inoculated internode. Splitting the inoculated internode longitudinally, the tissues about 

 the needle-pricks are discolored, but the discoloration does not spread for more than 0.125 inch in 

 either direction. All the leaves are green in this cane, and from the top to the bottom it seems to be 

 perfectly healthy. On dissecting out the terminal bud, however, the very youngest leaves are dead, 

 but this injury, I think, has been done by the ventilating apparatus in the greenhouse. 



No. 40. This cane is 7 feet long and about 1.25 inches in diameter. The basal 15 leaves are 

 entirely dead and brown, while the upper leaves are gradually dying from the tip toward the base. 

 The terminal bud is entirely dead and brown. There is a large quantity of yellow gummy ooze 

 exuding from the base of this stem, which has been cut about 2 hours. It is 10 internodes below the 

 one inoculated. This cane was carried to the laboratory in Mo, where it was dissected. 



LABORATORY NOTE. The yellow ooze from many bundles has coalesced at the basal cut, so that 

 the surface is just a mass of yellow gum. All of the leaves are in an unhealthy condition, some being 

 entirely dried up, while others are drying from the tip down and along the margins. The leaves 

 enveloping the terminal bud are all dead. On sectioning there is abundant bacterial ooze from prac- 

 tically all bundles in all the internodes below the inoculated internode. The ooze does not show 

 much in the upper internodes, however. It runs out completely in the fifth above the point of inocu- 

 lation. Plates were poured from this cane. Sections of the stem were saved in alcohol and photo- 

 graphs were made (plate 5). 



Inoculation No. 41 could not be found. The label was lying on the ground. 



No. 42. This is a cane about the same size as No. 39. It seems to be very healthy. The inter- 

 nodes are from 6 to 8 inches long. The upper leaves are all healthy except the topmost ones, which 

 have been torn by the ventilating apparatus. At the basal cut there are at least 1 5 or 20 discolored 

 bundles. These run all the way up to the top of the stem apparently as many at the top as there 

 are at the base. The discoloration (red stain) of the vascular system is much more marked at the 

 nodes than in the internodes. When the stem was split longitudinally, some of the bundles were 

 observed to be red, while others were yellow. 



A large number of the bundles in this stem, when examined microscopically, showed enormous 

 masses of bacteria. Plates were poured from this stem. 



No. 43*. A medium-sized cane, about 5 feet high and 1.25 inches in diameter at the base. 

 There is no sign of discoloration in the tissues in any of the basal nodes. From top to bottom the 

 stem seems to be perfectly sound. The inoculation has not taken at all. 



No. 44*. This is a very large cane, about 9 feet in height and i .25 inches in diameter at the base. 

 The cane externally seems to be perfectly healthy. All the leaves are green from the bottom to the 

 top. The terminal bud is perfectly sound. On sectioning the inoculated internode, the discolor- 



fThis row of cane was labeled " Common Green, " but it looks very much like " Striped Green." The labels may 

 have been mixed in the transplanting. 



