FIELD CROPS 379 



I 



of large and small grains, concluded that the individual plants from 

 large grains are larger than the individual plants from small grains, 

 but made no comparison of yields under field conditions. 



The Kansas Station, after four years' work with light, heavy, 

 and unseparated seed, secured slightly increased yields in favor of 

 the heavy wheat when the light and heavy were compared, but no 

 difference when the ordinary unseparated stock was compared with 

 the heavy. 



At the Indiana Station, for four years, large seed gave an aver- 

 age yield of 1.47 bushels more than small seed. In order to obtain a 

 census of opinion upon this very important question, a circular letter 

 was addressed on December 31, 1906, to the various experiment sta- 

 tions in the central and western states, asking for an opinion on the 

 following questions : 



1. Have you any experience or reliable data which would prove 

 conclusively that the continued use of the fanning mill to remove 

 the shrunken and very light grains from wheat will tend to increase 

 the crop? 



2. After the light, shrunken and shriveled grains and foreign 

 matter have been removed from the wheat, is there any evidence 

 that further separation of the same according to the specific gravity 

 of the grains, that is, into heavy and light seed, and this practice con- 

 tinued for a number of years, would affect one way or the other the 

 yield of the crop? 



Answers from eight were received and were uniformly to the 

 effect that, except for the purpose of removing foreign matter and 

 weed seeds, both of which would be troublesome in securing a uni- 

 form stand, or obnoxious weeds which might infect the land, there 

 was no good evidence that the continuous use of the fanning mill 

 would either improve the quality or increase the quantity of the 

 yield. 



The only rational method of improving the yielding power of 

 our seed wheat seems to be through some system of plant selection, or 

 by plant breeding, as it is now called. Experiments which have been 

 in progress for years have shown a marked difference in the yield 

 and quality of wheat from different plants. 



The discussion in this bulletin refers to the permanent results 

 which may be expected from the use of a fanning mill, and in no 

 way discourages the use of a fanning mill or screen for removing 

 obnoxious weed seed. Also where a large proportion of the seed grain 

 is shrunken, immature or damaged, it will no doubt increase the fol- 

 lowing crop to remove the poor seed. (U. Nebr. A. E. S. 104.) 



SEPARATION OF SEED BY THE SPECIFIC GRAVITY METHOD. 



The specific gravity method of seed separation consists in the 

 immersion of the seed in liquids of varying density. These different 

 densities are obtained by the addition of various quantities of salts 

 or other agents by which the specific gravity of the liquid is increased 

 or decreased, as desired. When different kinds of seeds are immersed 

 in these solutions, those which are lower in specific gravity than the 

 liquid in which they are placed will float on the surface. The 



