122 ''Sleepy Disease" of the Tomato 



In studying Verticillium wilt, Van der Lek has suggested (19) that 

 in this disease of the cucumber the fungal hyphae enter and kill 

 the parenchymatous tissues of the leaves. Klebahn studying the 

 Verticillium wilt of dahUa{i2), Haskell the Fusarium wilt of potatoes (U), 

 and Brandes the Fusarium wilt of banana (2) have all suggested the 

 excretion by the fungus of a toxic substance, which is carried up the 

 vascular bundles and kills the plant. This hypothesis gains a certain 

 amount of support from the investigations by Dixon (7, 8) and Haskell (ii) 

 on the kilUng of plants by various artificial means. 



In the present study it was found that the walls of the vessels are 

 stained brown and in longitudinal sections a brown gum-hke substance 

 is frequently noticed hning the lumen and blocking up the vessels. In 

 the process of staining this is washed away, but it is readily seen in 

 fresh material. The similarity between the colour of this gum-like 

 substance and that of the liquids in some old culture tubes, led to 

 an examination of culture hquids. Cultures of Verticillium in Dox's 

 solution with 20 per cent, saccharose showed a distinct yellow colour in 

 the liquid. The fungus was therefore grown in this solution for 30 days, 

 when the hquid, which was appreciably yellow, was filtered and used in 

 the following experiments : 



A. Erlenmeyer flasks were set up with 100 c.c. respectively, of the 

 following solutions: 



Series 1. Five flasks of filtrate from cultures. 



,, 2. Five flasks of filtrate heated for five minutes at 100° C. 



,, 3. Five flasks of sterile medium. 



,, 4. Five flasks of sterile water. 

 Tomato seedlings 5 inches high were cut off under water near the 

 roots, and placed one per flask in the above series. In series 1 the plants 

 wilted in 17 minutes; in series 2 and 3 after 2 hours; while in series 4 the 

 plants were perfectly turgid after 24 hours. As the plants in series 3 

 showed wilt in 2 hours, it was evident that exosmosiS was taking place, 

 so the experiment was repeated with the liquids diluted to three times 

 their bulk with sterile water. In this case a definite wilt was produced 

 in series 1 in 42 minutes and slight wilting in series 2 in 95 minutes which 

 did not increase up to 24 hours. No wilt appeared in series 3 and 4 even 

 after 24 hours. 



B. To 1000 c.c. filtrate and 1000 c.c. sterile medium respectively, 

 absolute alcohol was added. A cloudy precipitate formed and the solu- 

 tions were allowed to stand until the precipitate settled to the bottom, 



