STEWART'S DISEASE OF SWEET CORN (MAIZE). 1 13 



writer controlled the cultures used and made notes on the results. The inoculations were 

 made by Miss Alice C. Haskins, one of the laboratory assistants. In this case all of the 

 plants were inoculated by needle-punctures, mostly in the blades of upper leaves. No 

 hypodermic injections were made. Owing to unavoidable delay on her part the plants 

 were not inoculated until they were about half-grown, i. c, 3 weeks later than I had planned, 

 and when it might be presumed that they would be able to complete their growth before 

 any general infection of the plant could take place. 



The needle-pricks were made March 10 to 14. The cultures used were grown on slant 

 agar and on potato and were subcultures from an isolation of the previous year. Altogether 

 57 plants were inoculated 32 sweet-corn and 25 field-corn. With one or two exceptions, 

 two leaves were inoculated on each plant. The bacterial slime was mixed with water; a 

 portion of this was spread on the leaf -blade with a platinum loop and punctures were made 

 through the smeared portion ; a little more of the fluid was then spread over the punctured 

 area. The following notes were made by the writer : 



March 20, 1905. A few of the plants show slight indications of infection streaking down from some of the pricks. 

 One plant also shows two narrow water-soaked stripes near the pricked area, but not centering in any of the pricks, as 

 though it were stomatal infection due to the material placed on the leaf. This was visible the day before yesterday and 

 this morning. Not visible this afternoon. 



The sweet corn is in full blossom. Some of the field-corn plants are coming into blossom, others not. 



April 8, 1005. The first case was brought in to-day from hot-house No. 4. It is plant No. 18. Two inoculations 

 were made on the base of two uppermost leaf-blades, which are now dead, together with the whitish, dwarfed male 

 inflorescence. The plant, which is a small one, bears 2 small ears and 3 green leaves. The progression of the dry 

 leaves is the reverse of that observed in the field, but otherwise the disease looks typical. On cutting open the base of 

 the stem it is free from infection, but the bundles in the green leaf-sheaths of the inoculated leaves contain a pale yellow 

 ooze, which under the microscope is bacterial and of the typical appearance. The yellow slime occurs also in the vessels 

 of the upper part of the stem, mostly in the peripheral bundles. This plant is one of the sweet corns. It was inocu- 

 lated March 13, from a potato culture (tube 1, March 10). The plant has shown signs of the disease for 4 or 5 days 

 '. e, dry leaves and a white top. The inoculation took place just before flowering time. 



April 29, 1905. A majority of the inoculated plants show dead stripes in the pricked leaves. In some cases the 

 entire pricked leaf is dead. Quite a number of the plants are dead at the top. 



May 1, 1905. Plant 19. Bacteria in vessels of the stem 18 inches from the top. Top dead. All the basal leaves 

 are green. 



Plant 20: Basal leaves green, only the pricked ones are dead. Top dead and white. Bacteria present in stem 18 

 inches from the top. 



Plant 23 : The upper three leaves of this plant which were inoculated now have dead stripes. All the other leaves 

 are sound. Top dead. No bacterial ooze visible with hand-lens in cross-section of upper part of stem. Cut it in three 

 places. . 



Plant 33: Leaves above and below pricked ones are green. One pricked leaf is dead. The other is dying. Bac- 

 teria not visible in stem under hand-lens. 



Plant 37: One pricked leaf is dead and two-thirds of the blade of the other. All the other leaves are healthy. 

 Bacteria are not visible in the upper part of the stem, with the hand-lens. 



The above-mentioned 5 plants are sweet corns. 



May 8, 1905. Four plants were cut out this morning and examined. 



No. 2 : The middle, inoculated leaves are now dead. Their sheaths are infected by the bacteria. The top leaf is 

 green. The male inflorescence is dead. The basal leaves are green. The middle portion of the stem contains the 

 yellow bacteria in some abundance. 



No. 5 : The upper leaves and top of this plant are dead. The lower leaves are green. Cross-sections of the stem 2 

 feet from the top of the plant show a vellow ooze in a few of the bundles. 



No. 27: The male inflorescence is dead, but it bears some kernels of ripe corn, so that it may have died naturally. 

 The top of the plant and the basal leaves are green. The inoculated leaves are dying. There is a visible stem infection 

 only near the junction of the inoculated leaves and this infection is confined to a few bundles. 



No. 35 : The male inflorescence and the upper 4 leaves are dead. The lower leaves are green. The yellow bac- 

 terial ooze is distinct in a few bundles in the upper part of the stem. 



Nos. 2,5,27, and 35 are sweet corns. As in the plants already cut and described, the 



stem-infection is slight in comparison with the stem-infection in the plants inoculated 3 



years ago in the seedling stage by way of the water-pores. The inoculations were made too 



late in the growth of the plants. 



Mav 13, 1905. Five plants were cut out and examined to-day. 



Plant 17- Top dead; base green; pricked leaves dead. The bacterial infection is present but slight. 



Plant 22 : Top dead; pricked leaves dead; the lower leaves green; stem green. On cross-section of the upper part 

 of the stem S or 10 bundles show a distinct yellow ooze. 



Plant 24: Top dead, including inoculated leaves. Slight infection of the stem, that is, yellow bacterial ooze from a 

 few bundles, mostly peripheral ones. . 



Plant 26: Top dead; pricked leaves dead; lower leaves green; stem green. A few bundles in the upper part of the 

 stem show a yellow ooze on section. . 



Plant 5 1 (field corn) : Cut out and dissected. No indications of stem-infection when examined under hand-lens. 



