24 BACTERIA IN RELATION TO PLANT DISEASES. 



whitening in stripes along the margin. Four leaves show these signs and a fifth shows median white 

 striping with dead brown patches toward the base, in the stripes. 



(9) Plant 9 is about 4 feet high and about half an inch in diameter at 18 inches above the ground. 

 It bears 14 leaves. Leaf g a, which is about 5 feet long, is dead throughout, except possibly the 

 extreme base of the sheath. 



Leaf g b, which is about 5 feet long, is dead throughout, except a small portion of the basal part 

 of the midrib and a part of the sheath. The plant shows distinct secondary signs. One entire upper 

 leaf, which is about 6 feet long, is dead throughout. Another large leaf is drying out on one margin 

 for a distance of 3 or 4 feet and the apex is flabby. A third leaf is dry from the base upward to the 

 tip on one side. A fourth small central leaf is flabby. 



(10) No. 10 is a small plant. Height 3.5 feet; diameter a foot from the ground 0.25 inch; 

 number of leaves 11. Inoculated leaf 10 a is dead throughout, including all the visible part of the 

 leaf-sheath. Leaf 10 b is dead throughout, including all the visible part of the leaf-sheath. The 

 top of the plant is also dead ; that is, three leaves. Three additional upper leaves are dying in stripes. 

 Photograph made. It is the smaller of the two plants photographed to-day (April 3). 



(11) No. 11 is nearly an inch in diameter at 1 foot from the ground. It is about 5 feet high. 

 It bears 14 leaves. Leaf 1/ a is dead throughout, unless it be a portion of the leaf-sheath. Inocu- 

 lated leaf 11b, which is about 6 feet long, is dead and dry throughout, except the basal 1 foot of the 

 midrib and a portion of the middle part of the sheath. This plant also shows conspicuous secondary 

 signs. Of the upper leaves, five are distinctly striped and the two uppermost are flabby. One long 

 leaf is dead throughout, except the basal 1 foot, and even this part is dead on the margin, the midrib 

 being the only live part. There is conspicuous etiolation of the margins of some of these leaves. 

 This sign precedes the drying out. There are also distinct, narrow, brown or red-brown interrupted 

 stripings in the basal portion of the etiolated part. One of these upper leaves was pricked with about 

 150 needle-pricks (sterile) at 3 feet from the leaf -sheath on March 2, as a check: No striping has 

 resulted. The needle-punctures themselves have a narrow white margin around them but the tissue 

 between the pricks, which are set in close together, is still bright green. I mean by this that the 

 pricked area is not over 1.25 inches broad (width of the leaf) by 1.5 inches long, and yet with all this 

 number of punctures in it there has been no general death of the tissue, and no up or down striping 

 such as took place within a few days in case of every one of the inoculated leaves. 



(12) Plant 12 is about 3.5 feet high; the diameter at 1 foot from the ground is about 0.5 inch; 

 it has 12 leaves. Inoculated leaf 12 a is dead from the tip down a distance of about 3 feet. From 

 there to the sheath, a distance of another foot, the midrib is green, but the margins are dead. 



Inoculated leaf 12 b, which is 4 feet long, is dead in the upper 1 foot and dead on both margins 

 all the rest of the way down to the sheath, but the midrib in this part is green. This plant also shows 

 distinct secondary signs on five leaves. One uninoculated leaf is dead from the apex down a distance 

 of 3 feet. Another is dead on both margins for a long distance down and also has reddish-brown, 

 narrow, interrupted stripes in the green part farther down, and a third has conspicuous etiolation 

 near the midrib on one side, and there are a great number of narrow interrupted reddish-brown spots 

 in this etiolated part. 



The two rows of cane to either side of this row are at least 3 feet higher and are altogether 

 thriftier, showing no signs whatever comparable to those just described (fig. 15). Neither of these 

 vigorous rows to either side are outer rows, but they are at the same time not of the same variety, 

 one of them being Purple Striped cane and the other Striped Green cane. 



At the end of 2.5 to 3 months all of the inoculated leaves and some other large leaves 

 were shriveled and the tip of the terminal bud had gone over into a bacterial decay. All of 

 the inoculated plants succumbed. The leaves at this time were not all dead and the well- 

 developed lower part of the stem was green and sound externally. The internodes were 

 shortened and the basal buds were either much swollen or beginning to push. The plants 

 stood in a dry house and had not received an excessive amount of water. I )uring the pro- 

 gress of the disease some shoots and roots pushed out from the nodes at the base of the cane. 



When the first signs appeared on the inoculated leaves one was removed and thin cross- 

 sections were examined under the microscope for the presence of the bacteria. These were 

 found in great numbers in the bundles about 18 cm. above and for some distance (10 cm., 

 perhaps) below the pricked area. Later the bacteria became very abundant in the stems. 

 They were also found in bundles in the etiolated parts of the uninoculated leaves. Plates 

 of nutrient agar poured from several plants and from different heights in the stem yielded 



