100 BACTERIA IN RELATION TO PLANT DISEASES. 



tion extends as far as the base of the cob and runs out into some of the husks around the cob. In the 

 main axis visible infection ends just below the male inflorescence. 



XXI. Cut 3 inches from root : A great many bundles are infected. Base cut longitudinally : 

 Lower nodes brown; bundles of the internodes either brown or yellow; roots slightly infected near 

 their juncture with the stem. All nodes infected; lower, brown, grading into yellow in the upper 

 part of the stem. Infected visibly to just below tassel. In the cob, the base and a few bundles 

 further up are visibly infected. 



XXII. Basal parts of stem show yellow bundles. 



XXIII. Cut 3 inches from roots : Bundles packed with yellow slime. Split longitudinally (basal 

 part) . Browned in nodes and some yellow bundles in the internodes. Upper nodes as in XXI. 



XXIV. Basal nodes brown in longitudinal section (3 inches above root). No indication in 

 these lower internodes of yellow bundles, but numerous plainly yellow bundles in an internode 6 inches 

 above the roots. 



Plants XXV to XXXV were brought in and examined on October 17. All of the plants 

 were well provided with roots which looked sound on the surface. The stems were green 

 in all cases and normal in external appearance, but the leaves were shriveled and the tops 

 were dried out as well in those standing as in those accidentally broken off. The cause of 

 the disease was not apparent. 



XXV. Cut close to root: No plain evidence of infection. This plant was broken off accident- 

 ally, and therefore brought up at this time. One of the basal nodes is brown. No distinct evidence 

 of the disease in the internodes. This brown node was examined microscopically with doubtful 

 results. 



XXVI. Brought in because broken off at root. Section cut about 3 inches above the root : In 

 the internode no distinct signs of disease, but three nodes above it are brown. In the internodes 

 between there is no distinct yellowing of the bundles. Infection, if any, is slight. Several of these 

 plants seem to confirm Stewart's statement that the brown stain is not a sign of the disease. Later, 

 found a yellow slime-infested bundle in one of the basal internodes. 



XXVII. A few brown vessels in an internode about 2 inches from base of the stem. The lower 

 nodes are brown. Infection slight. One node 8 inches up, one node a foot up, and a third node 16 

 inches up are brown. A hasty examination shows no appearance of infection in the internodes 

 between these nodes. 



XXVIII. One of the lower nodes slightly browned. No evidence of disease in internodes. The 

 upper nodes look all right. Hasty microscopic examination gave doubtful results. Basal part slit 

 through, shows brown nodes; no evidence of disease in the internodes. 



XXIX. Section 3 inches from base of stem contains a great many bright yellow bundles. Leaf- 

 sheath shows yellow spots corresponding to masses of bacteria which have oozed out of the bundles 

 into the parenchyma. Slit longitudinally, the base of the stem shows brown nodes and yellow 

 bundles in the internodes. The disease extends very plainly two-thirds of the way up the stem and 

 runs out into the cob, and occurs to a slight extent in the remainder of the stem. 



XXX. No plain evidence of infection except the brown stain. Base slit through shows brown 

 nodes. No evidence of yellow ooze in the internodes. 



XXXI. Cut 3 inches from the root, the bundles show a yellow ooze. Longitudinal section 

 through this base shows brown nodes with some yellow bundles in the internodes ; not in the ear. The 

 browning is less conspicuous in the basal nodes than in some of the other plants. The nodes higher 

 up are not brown. Visible infection is confined to the basal parts. 



XXXII. Section 3 inches from base shows in the internode numerous bundles from which there 

 is a yellow ooze. In a leaf-sheath about 9 inches up, the bacteria have escaped from the bundles 

 and formed bright yellow patches in the parenchyma. Corresponding to this escape from the 

 bundles is a water-soaked patch 2.5 inches long by 0.75 inch broad (saved in alcohol, flat between 

 glass slides) . The yellow slime is also in the base of the ear. The bacterial ooze comes out of bundles 

 close under the tassel. Basal part of the stem slit shows brown nodes, and yellow bundles in some of 

 the internodes. 



XXXIII. This plant, which is about 4 feet high, has one good-sized ear and several small ones. 

 Cut about 3 inches from the base, many of the bundles show yellow bacterial ooze on cross-section. 

 Nothing in the two abortive ears. Longitudinal section through the basal 3 inches of the stem shows 

 3 brown nodes with yellow bundles in the internodes. The infection extends the whole length of the 

 stem, the basal half dozen nodes being brown and the upper ones yellow. The internodes show yel- 

 low stripes, corresponding to diseased bundles, for a long distance up the stem. The leaf-sheaths of 

 leaves i foot to 2 feet above the root also have the bacteria in their bundles. 



