WILT OF CUCURBITS. 21 7 



FIELD. HOTHOUSE. AND LABORATORY NOTES. 



Early Studies. 



The work of the first few months was thrown away, principally because I did not know 

 how to proceed, my technique being defective. Up to November 24, 1893, I had isolated 

 five or six organisms as follows but had not obtained infections with any, and was very 

 much at sea after a great deal of hard work: 



(1.) A slow growing white organism on streaks and in poured plates. In the latter there were 

 very numerous colonies but small even after months. 



(2.) A very rapidly growing white organism. It runs ail over the plate in two or three days and 

 is more or less dendritic. Spore-bearing one oblong spore, central or at one end. 



(3.) A greenish organism which colors the agar. Much faster growing than 1 but slower than 2. 



(4.) An orange colored organism with crenate edges and in old specimens with radial fissures. 

 It grows faster than 1 . 



(5.) A faint pinkish growth. 



(6.) A rapidly growing, wrinkled organism, color dirty-Isabella. 



The form 1 was undoubtedly the right organism, and probably the only one obtained 

 from the interior of the plant. The others were undoubtedly intruders dragged in from the 

 surface of the plant when I made my cross-sections, but I did not know it at the time. Sub- 

 sequently I learned how to exclude outside organisms by the use of hot instruments. 

 After that, labor was lightened, and inoculations with the right organism soon threw a flood 

 of light over what had hitherto been an obscure subject. 



The only genuine infections I had obtained up to this date were on several squash 

 leaves by direct transfer as described below. A few earlier supposed infections on cucumber 

 leaves obtained with the organism No. 6, did not progress beyond areas which had this 

 organism plastered on them, and were undoubtedly not true infections but only suffocation 

 spots due to the overwhelming mass of material used, i.e., to defective methods of pro- 

 cedure with some soft-rot organism, or potato bacillus. 



Squash Blight. 

 The following observations and experiments were made at Hubbardston, Mich., in 1S93. 



(1.) September 2: Several 9-foot vines became infected several weeks ago in the main axis, 

 naturally, and have lost a dozen to 15 basal leaves by the blight. All the foliage is dwarfed and 

 yellowish. The foliage shows wilt in the daytime with partial recovery at night, the squash plants 

 being more resistant than cucumbers. One of the striking signs is the formation of a short branch 

 in every leaf axis and the development of a flower cluster often a dozen buds. One 9-foot vine bore 

 43 branches and several hundred flower buds. This strongly suggests what occurs in orange blight 

 in Florida. The uninjured vines are very green and thrifty, 12 to 14 feet long. I know these vines 

 have been infected several weeks, from the general appearance, which has changed only slowly in the 

 last 8 days; from the old dried up appearance of the blighted leaves in the center of the hill; and from 

 the ease with which I get the milk-white bacterial ooze on the cut surface of basal branches near the 

 main axis and also a foot or more away from it. This sticky ooze, appears abundantly on the cut 

 surface over the fibro-vascular bundles in as short a time as 2 to 4 hours when placed in moist air 

 with the bottom of the inch-long segments in water. No such exudate appears on the cut stems of 

 the healthy plants. September 1 1 : The vines are still living and look as if they would live 2 weeks 

 longer, but many leaves have died and all are yellow or dwarfed. 



(2.) Four squash flowers were inoculated September 1, from the white ooze. The germs were 

 thrust down upon the nectary and the mouth of the flower was tied up. August 30, two squash- 

 flowers were so infected and 2 days later one was examined and the whole nectary disk found dead 

 and one uniform colony of germs. September 7: Germs grew in the nectary; the stems were not 

 infected, or at least no secondary signs appeared during my stay. 



(3.) Bacteria from the cut ends of a squash-stem were pricked into two leaves (two vines), on 

 August 30, using a sewing needle. Up to September 2, no blight. When pricked the blades of these 

 leaves were 4 inches in diameter. Later: Typical blight appeared in both leaves in about eight days. 

 (See under No. 10.) 



