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JOURNAL OF AGRICULTURE OF P. R. 



iu quantities of twenty grams or more severely burned the plants, 

 and even with mature cane severe injury resulted. 



Hence it was found impossible to use gasoline as a sub:^titute 

 or as an adulterant for carbon bisulphide. The great increase in 

 the cost of gasoline at the present time would of course preclude 

 its use, even had it proved to be non-injurious to plant life. 



Potassium cyanide. 



In view of the deadly nature of potassium cyanide and of i-e- 

 ports of its successful use in controlling certain forms of subterra- 

 nean insects, it seemed desirable to try it out against the white gru])s. 

 Experiments were accordingly carried out in which potassium cya- 

 nide in both liquid and crystal form was applied in various amounts 

 and at varying depths in the soil, around the roots of the sugar cane. 



The - potassium-cyanide solution was prepared by dissolving two 

 hundred grams of the crystals iu a liter of water. Five grams of 

 the crystals w'ere thus equivalent to tw-enty-five cc. of solution. For 

 purposes of comparison equivalent amounts of potassium cyanide 

 were used in both experiments. The following tables show the i-e- 

 sults obtained : 



Experiment V. — Experiment with Potassium Cyanide in Liquid Fonn. 



Experiment VI. — Experiment with Potassium Cyanide in Crystal Form. 



From the abovc^ tables w^e see that there was very little difference 



