No. 4.] MASSACHUSETTS WEEDS. 275 



the plant must be taken into consideration. Various kinds 

 of cultivation have been devised to meet the requirements 

 of weeds, and an attempt has been made to kill weeds by 

 powerful electrical machines. Such appliances are not prac- 

 tical, as the enormous voltage of twenty thousand was re- 

 quired to kill the plants. Could a current be made to pass 

 through the plant from the tip of the root to the tip of the 

 stem a much smaller voltage could be used. I have killed 

 small plants in the laboratory with an electrical force equal 

 to forty or fifty volts when the current was applied in this 

 manner. Even supposing such appliances could be devised 

 on a simple and cheap scale, so as to be utilized, they would 

 be of no value when applied to cultivated crops, inasmuch 

 as one of the blessings of weeds is that they remind the 

 gardener that it is time for his crops to be hoed, and any 

 appliance which fails to stir up the soil would be an injury 

 rather than a help. 



Other methods have been tried for weed eradication with 

 more success. The application of chemicals to freshly cut 

 roots, or at the base of the stem, has been used in some in- 

 stances with success. For this purpose experimenters have 

 resorted to the use of coal oil, crude sulphuric acid, salt, 

 strong brine and carbolic acid. A few drops of carbolic acid 

 applied with an ordinary machine oil can is considered the 

 best method that has been devised for killing weeds with chem- 

 icals. Salt has been used with some success on the Canada 

 thistle and golden hawkweed. Experiments upon the golden 

 hawkweed in Vermont with salt at the rate of three thousand 

 pounds per acre have proven effectual, and at the same time 

 have increased the yield of grass. 



In the case of biennials, cutting the root below the crown 

 usually kills them ; but occasional mowings induce them to 

 send up numerous stalks from their roots, which, if not cut, 

 will come to maturity and produce seed. The wild carrot 

 affords an example of a biennial, and outside of hand pulling 

 repeated mowing is about the only practical method which 

 can be employed. This prevents the plant from maturing its 

 seed, and also by checking assimilation starves the plant out. 



Many root-stalks are successfully killed by exposing them 

 to the direct action of the sun in summer or of frost in winter. 



