434 PhyHiad ('/iin((cf<i-isfirs and Mdh'ii;/ Qinditi/ 



wheat samples grown in Minnesota luivc been examined which displaced 

 from 7-2 to 25-2 cubic centimetres per 1000 kernels. Greater extremes 

 than these would doubtless be found in working with a larger number 

 of samples. These variations are due to environmental influences, 

 particularly those which affect the rate of photosynthesis just preceding 

 tiio i-iponing of tiic plant. Soil moisture, humidity, sunshine, tem- 

 perature, and winds are most potent in this regard. Severe rust and 

 scab infections result in the production of shrivelled, light-weight 

 kernels. 



Similarly there are wide variations in the percentage of flour 

 which can be produced from wheats of varying plumpness. In esti- 

 mating the relative percentage of flour which can be milled from different 

 samples of wheat, the kernel volume and the density are believed to 

 be better indices than the weight per bushel. The latter is influenced 

 not only by the actual volume of the kernels but by their relative 

 length : width ratio, and other factors affecting the manner in which they 

 pack together. While the relation of the two factors mentioned to 

 milling yield is not exact in all cases, certain experiments which we have 

 made show them to be of considerable value in estimating the quality 

 of wheat from this standpoint. 



Table II. Physical characlerislics of cotnposite samples of northern 

 spring wheat grades and the yield of flour obtained from them in 



milling. 



Table II shows the results of one series of tests made to determine 

 the relation of kernel volume to the percentage of total flour obtained 

 in milling. A fairly regular decrease in flour yield was observed as the 

 kernels decreased in size. The samples employed in this case w'ere 

 composite No. 1, No. 2, No. .'5. and No. 4 northern spring wheat, repre- 

 senting the average of these grades in the Minnesota markets. Similar 

 results were obtained in milling other wheat samples of varying plump- 

 ness. The milling tests were made in the experimental roller mill at 

 this station. The method employed is described in Minnesota 

 Agricultural Station Bulletins, Nos. 131 and 113. While the flour 



