March 20, 1903.] 



SCIENCE. 



457 



former color. Casein is slowly precipi- 

 tated and finally redissolved. No gas is 

 produced from any medium. 



The paper was illustrated by fifty lan- 

 tern slides showing the location of the bac- 

 teria in the tissues and illustrating the 

 morphology and cultural characters of the 

 organism. 



Completed Proof that P. Stewarti is the 

 Cause of the Sweet Corn Disease of 

 Long Island: Dr. Brwin F. Smith, 

 Department of Agriculture. 

 In the winter of 1897-98, Stewart de- 

 scribed a disease of sweet corn from Long 

 Island which he attributed to a yellow bac- 

 terium that was very abundant in the ves- 

 sels. This organism Smith subsequently 

 named P. Stewarti. Stewart's infection 

 experiments were inconclusive partly be- 

 cause made in a locality where the disease 

 occurred naturally and soon appeared on 

 the check plants, and partly because not 

 made in the most natural way. 



In the summer of 1902 the writer visited 

 Long Island and obtained pure cultures of 

 the organism. With these about 500 sweet 

 com plants of several varieties were inocu- 

 lated, all during the seedling stage. Part 

 of these plants were exposed to infection 

 by placing the bacteria in drops of fluid 

 oozing from the water-pores at the tip of 

 the leaf, part by shaking up slant-agar 

 cultures in sterile water and spraying this 

 on the plants in a fine mist, during the 

 period when they were extruding water 

 from their leaf -tips. Both methods yielded 

 good results. The first shriveling of tissue 

 was at the tips of the inoculated leaves. 

 Typical constitutional symptoms appeared 

 in a few plants during the first month, but 

 most of the cases developed the second and 

 third month when the plants were several 

 feet high. In such it was common to find 

 the vascular system plugged with this yel- 

 low bacterium in practically pure culture 



all the way from the basal nodes to the top 

 of the plant, four and one half feet in some 

 cases. The nodes of such plants were 

 browned inside very decidedly, especially 

 the basal ones; the internodes within were 

 generally white, with yellow bundles from 

 which the bacteria oozed abundantly on 

 cross-section. Frequently 150 or more 

 bundles would be occupied. More than 

 300 typical cases of this disease were ob- 

 tained, and many other plants would un- 

 doubtedly have shown symptoms had not 

 the experiment been cut short by a frost. 

 One of the first symptoms of this disease 

 is the whitening and death of the male 

 inflorescence. The leaf blades dry out one 

 after another until all are dry, while the 

 stem is still green. In this condition the 

 affected plants look as if frosted, and the 

 cause of the disease is not apparent until 

 the plants are cut open. 



This experiment, conducted in Washing- 

 ton, where the disease does not occur, shows 

 conclusively that wounds are not necessary 

 for infection, and makes it reasonably cer- 

 tain that natural infections take place as 

 a rule through the water-pores or ordinary 

 stomata in the seedling stage of the plants. 

 The vascular system is the primary seat 

 of the disease, but small cavities filled 

 with the bright yellow slime finally appear 

 in the parenchyma. The bacteria were 

 not confined to the stem but passed out into 

 the vascular system of the blades of the 

 middle and upper leaves and into vessels 

 of the husks and cobs. The paper was 

 illustrated by lantern slides. 



Opportunities for Study at the Minnesota 

 Seaside Station: Professor Conway Mac- 

 MiLLAN, University of Minnesota. 

 The speaker gave an account of the sur- 

 roundings of the station, the particularly 

 rich marine flora, and the advantages 

 offered for investigation in this compara- 



