CONTENTS 



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Page 

 Department Bulletin No. 1201. — Plants Tested for or Reported 

 to Possess Insecticidal Properties: 



Economic aspects of plant insecticides 1 



Methods used by the writers in preparing plants for insecticides 2 



Insects employed and methods of testing preparations against them__ 3 



Results obtained by the writers 5 



Discussion of the more important results obtained 5 



Comparative results djscussed 10 



Discussion of the less important results obtained 21 



Catalogue of plants tested for or reported to possess insecticidal 



properties 24 



General summary : 53 



Conclusions 54 



Literature cited 54 



Index of botanical and common names of plants catalogued 59 



Department Bulletin No. 1202. — Tractors and Horses in the 

 Winter Wheat Belt, Oklahoma, Kansas, Nebraska: 



Description of areas 4 



Farms operated with one tractor and horses 5 



Size and age of tractors 6 



Number of work stock 7 



Work done with tractors 8 



Work done with horses 19 



Horse labor equivalent of tractor work 22 



Proportion of work done with different forms of power 23 



Work stock needed in addition to tractor 26 



Cost of keeping work stock 28 



Cost of using tractors 32 



Reliability of tractors 38 



Annual cost of power for drawbar work 38 



Changes after purchase of tractor 43 



Owners' opinions regarding use of tractors 49 



Farms on which tractors were not owned 50 



Number of work stock 50 



Cost of keeping work stock 53 



Annual cost of power for drawbar work 54 



Changes between 1918 and 1921 55 



Opinions concerning tractors 56 



Cost of power and man labor for different operations 56 



Farms on which no horses were owned 57 



Farms on which two tractors were owned 58 



Department Bulletin No. 1203. — Experimental Production of 

 Straw Gas: 



Introduction 1 



Straw-gas producing plant 1 



Operation of experimental plant 4 



Results of experimental work 4 



Probable annual consumption of gas on average northern farm 5 



Liquefying and compressing straw gas 6 



Straw gas for automotive power 6 



Use of baled straw 6 



Value and utilization of by-products 6 



Impracticability of experimental plant 7 



Improvement of experimental equipment 9 



Impracticability of destructive distillation of straw and similar 



material on farms 10 



79499c— 28 3 



