STEWART'S DISEASE OF SWEET CORN (MAIZE). IOI 



XXXIV. Cut about 3 inches above the root, numerous bundles are brown and others show a 

 yellow ooze. Split longitudinally, the base of the stem shows brown nodes with internodes having 

 bright yellow bundles and brown bundles. The first 4 nodes above the basal 3 inches are brown. 

 The disease extends visibly up to the tassel. It also extends into the base of the ear, but only to a 

 slight extent. The bacteria are abundant in the middle internodes, some of the bundles being brown 

 and others bright yellow. Further examination shows the bacteria as far up as the middle part of the 

 male inflorescence. The bacteria are also in a leaf-sheath midway up the stem. 



XXXV. Cut at 3 inches from root, bundles full of yellow slime. Cut a foot above the root, 

 bundles full of yellow slime. Cut 2 feet above the root, no evidence of bacterial masses under a hand- 

 lens. Split longitudinally through the base of the stem, the lower 3 nodes are brown in the center, but 

 the outer portion of the stem is white, as has been the case in all of these plants. The lower inter- 

 nodes have some brown bundles and some yellow ones. The bacteria extend up into the base of a 

 good-sized ear. The nodes above the first 3 vary from brown to yellow, the lower ones being brown 

 and the upper ones yellow from the presence of the bacteria. It is quite clear that the infection was 

 from below upward, i. c, the basal nodes are the worst affected. A second ear on the same plant 

 shows the disease in the basal part of the cob. The bacteria are present in the bundles of a leaf- 

 sheath 15 inches from the ground, and the node from which this leaf-sheath originates is yellow from 

 the presence of the bacterial slime. Also, in a leaf-sheath 2 feet from the ground, the bacteria are 

 present. Longitudinal sections through the central internodes show long yellow stripes, and in at 

 least one place the bacteria have escaped from the bundles and have made a yellow spot (cavity) in 

 the parenchyma (specimen saved in alcohol). 



Plants XXXVI to LI were brought in and examined on October 21. This bundle of 

 diseased plants gave no external indication as to the cause of the trouble. The drying out 

 of the leaves much resembled the effect of frost, but there had been no frost. When the 

 male inflorescence is not mentioned it was broken over. Photographs were made showing 

 the appearance of the stems in cross-section and longitudinal section, and also the appear- 

 ance of the diseased husks. 



XXXVI. Plant 3.5 feet high, stem green and sound externally, leaves dried up, tassel white 

 (dry), roots abundant and sound on the surface. This plant has two small ears, one of which is 

 infected at the base. Cut 3 inches from the base of the stem, several of the bundles show a distinctly 

 yellow ooze. Slit longitudinally, the six lower nodes are brown, those higher up are yellow (gummy). 

 The internodes toward the base of the stem show some black bundles and others which are bright 

 yellow. Internodes half way up the stem also show distinctly yellow bundles. The bacterial slime 

 apparently runs out toward the top of the stem, i. e., it is not visible under the hand-lens. 



XXXVII. Plant 3 feet high; male inflorescence dead. This plant branches at the base. Cut 

 the main stalk 3 inches from the ground; nothing definite in the internode. Slit the base longi- 

 tudinally, find 3 nodes decidedly black. No traces in the other branch. The basal internodes of the 

 main stem have large black streaks and have been injured by a borer. No evidence of yellow striping 

 in the bundles. This is the first plant observed to be affected by root insects. No evidence of bac- 

 terial disease farther up the stem. 



XXXVIII. Plant 3.5 feet high, broken over. The vessels of the bundles in internode 6 inches 

 up the stem are full of yellow slime. A large ear about 1 foot up shows no signs of the disease, but 

 there are numerous bright yellow bundles in the main stem under this ear. A smaller ear cut near 

 the base and slit longitudinally shows the infection in the lower part of it, in the bundles, in the form 

 of bright yellow stripes. The lower nodes are brown and the upper ones yellow for more than two- 

 thirds of the way up the stem. The bacteria can be traced in the internodes of the stem readily under 

 the hand-lens nearly to the top, the infection becoming less and less as one goes higher up the stem. 



XXXIX. Plant 4 feet high. Stem cut 3 inches from base, yellow bacteria very abundant in 

 the bundles. Slit longitudinally: The lowest 3 nodes are brown; the internodes have bright yellow 

 bundles; 3 of the nodes next higher up are brown, and then 4 more are distinctly yellowed. The bac- 

 teria are present in abundance in the base of a good-sized ear, but not in the kernel part as far as can 

 be seen with the naked eye. The disease disappears in the upper part of the stem. It is visible over 

 half way up the stem. The bacteria are abundant in the internodes in the lower and middle parts of 

 the stem as yellow stripes. They are in the bundles. In places bacteria have also oozed out of the 

 bundles into the parenchyma, making small bright yellow spots (dark in photograph). (See plate 9.) 



XL. Plant 4 feet high. Disease absent from base of one small ear. The bacteria are abundant 

 in the base of the larger ear, which is farther up than the smaller one. On cutting the pedicel they 

 ooze out immediately as bright yellow masses (samples saved in alcohol). The bacteria are also 

 present in the husks of the ear and have in some cases escaped from the bundles into the parenchyma 



