602 
Journal of Agricultural Research 
Vol. XXIII, No. 8 
/*£#C&/7?9G£ or/WATTS 
O /O 20 &O'*0J& dO&00&O/O0 
Fig. 7.—Graphic presentation of Table XVII, showing relation of diseased and nearly disease-free seed 
to the percentage of vigorous, semi vigorous, and weak plants produced, and to yield of marketable and 
unmarketable corn in bushels per acre. 
Tables XVIII, XIX, and XX give the results of similar experiments 
conducted on the Agronomy South Farm of the Illinois Agricultural 
Station at Urbana, Ill., during 1920, on very fertile soil (fig. 8), on soil 
of good average fertility, and on soil which has had 75 per cent of corn 
in the rotation for 13 years. 
et/&v£2.a or co/?// 
Fro. 8.—Graphic presentation of Table XVIH, showing the relation of moderately diseased and nearly 
disease-free seed to the percentage of vigorous, semivigorous, and weak plants produced, and to yield 
of marketable and unmarketable corn, in bushels per acre. 
In every ease there has been a marked increase in the field stand, per¬ 
centage of strong, vigorous plants, and yield of marketable com in the 
plots grown from nearly disease-free seeed. In Table XVIII the differ¬ 
ence in stand might account for the difference in total yield, but the 
difference in yield of marketable com must be accounted for in some 
other way. Figure 8 shows the relation of the increase in percentage of 
vigorous plants to the increase in yield of sound, marketable com. 
