140 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



Hop investigations have been productive of valuable results in 

 demonstrating the causes of failure to produce the best returns in 

 yield and quality, and have also led to the recommendation of 

 rational criteria for judging hops on the basis of their properties and 

 constituents rather than their geographic origin, with the hope of 

 removing certain forms of discrimination now made against Ameri- 

 can hops in the trade. Improved foreign varieties are being intro- 

 duced and progress made in the improvement of the yield and quality 

 ^f American hops. 



Studies of oil and perfumery plants have included the planting of 

 40 varieties of roses of imported types yielding the valuable rose oil 

 of commerce and the development of good commercial values from 

 raisin-seed waste and other oil-yielding residues, as well as from a 

 number of neglected plants. In this connection a new turpentine 

 substitute and a new linseed-oil substitute have been demonstrated. 



POISONOUS-PLANT STUDIES. 



Loco weeds, larksj^ur, wild lupine, death camas, and other poison- 

 ous plants have been responsible for enormous losses of stock m the 

 grazing regions of the West. These losses have been greatly reduced 

 through botanical surveys, and field and laboratory tests of suspected 

 plants, so that it has been possible to point out the harmful plants, 

 to recommend methods of avoiding poisonous-plant areas at the most 

 dangerous period of growth, and to devise and indicate methods of 

 treatment, antidoting, etc. 



PLANT PHYSIOLOGICAL INVESTIGATIONS. 



Advances in agricultural science have necessitated the broadening 

 of the work in physiological investigations to meet the demands for 

 fundamental knowledge of plant activities. The following are some 

 of the results of these studies: An accurate method for measuring the 

 oxidase content of plant juices, which has particular application in 

 determining physiological phenomena accompanying many types of 

 plant diseases; increased knowledge of the physiological conditions 

 affecting the keeping qualities of sweet potatoes in storage and a con- 

 sequent avoidance of the heavy annual losses from their rapid dete- 

 rioration ; a better understanding of the inorganic food requirements 

 of plants and of the influence on plant development of various ratios 

 of these inorganic constituents; and additional light upon existing 

 confusion as to the toxicity of certain molds occurring in spoiled foods 

 and the harmlessness of others of the same group, as the result of a 

 study of the metabolism of molds and of the conditions under which 

 they elaborate toxic products. 



