30 



MASS. EXPERIMENT STATION BULLETIN 195. 



It will be noted that the only substances which did not have an inhibiting 

 action on the growth were formaldehyde, sulfuric acid, and copper sulfate. 

 The rest of the chemicals applied did inhibit the growth of the tobacco, at 

 least in the amounts applied. 



A careful examination of the root systems of the plants in the different 

 plots was made by Mr. Krout of this department, who was in direct 

 charge of the root-rot work, and he reported as follows : — 



Table VII. — Comparison of Treatment with Thielavia Injection and Root 

 Development. 



Application 



(Pounds 

 per Acre). 



Thielavia 

 Infection 

 (Check In- 

 fection =100). 



Root 

 Development 

 (Check=100). 



Formaldehyde, 

 Sulfuric acid, . 

 Sulfur, . . . . 

 Mercuric chloride, . 

 Copper sulfate, 

 Ferrous sulfate, 

 Potassium permanganate, 

 "By-product A," 



4,800 

 2,400 

 1,200 



2,000 

 1,500 

 1,000 



100 

 80 

 25 



400 

 200 

 100 



1,000 

 500 

 250 



100 

 50 



4,000 

 2,000 

 1,000 



+ 

 15 

 15 



From the above it may be seen that the only substance used which 

 checked the- development of the root-rot, or controlled it to any great 

 extent, was the formaldehyde. The root growth also was apparently 

 stimulated by the lower concentrations. Sulfur, mercuric chloride, and 

 ferrous sulfate, while reducing the root-rot to some extent, had an injurious 

 effect on root development. The copper sulfate and sulfuric acid reduced 

 the amount of root-rot infection somewhat, and did not apparently, except 

 in the case of the greatest strength of sulfuric acid, reduce the root develop- 

 ment to any extent. 



These experiments were continued in the following year with comparable 

 results. It would seem that none of the substances used, with the excep- 

 tion of formaldehyde, were sufficiently beneficial in their action to warrant 



