BARLEY. 97 



tenance of produce, and great accumulation of potash in the 

 crops, where potash has been annually applied. Further, 

 the indication is, that the whole of the residue of potash sup- 

 plied during the first eight years on the plots where none has 

 been applied since, has been approximately exhausted during 

 the succeeding forty years. It is obvious, therefore, that Dr 

 Dyer will find new points of interest in the investigation of 

 the experimental wheat-field soils ; for the results will afford 

 illustrations, not only of mere exhaustion and accumulation, 

 but of effective residue as well. 



On what does Strength of Straw Depend . ? 



It will be appropriate to refer here to the bearing of ex- Silica and 

 perimental evidence on the question whether, as is frequently *^^ A< ^ 

 stated, strength of straw is dependent on a high percentage of 

 silica. Table 31 (p. 98) affords illustrations on this point. Table si 

 The upper division of the table gives results relating to ex P lained - 

 wheat, and the lower corresponding results relating to 

 barley. In the case of wheat five, and in that of barley 

 three, very different conditions of manuring are selected for 

 illustration ; and, for each condition as to manuring, results 

 obtained in bad and in good seasons are given. The particu- 

 lars indicating the character of the crops are — the percentage 

 of grain in the total produce, and the weight per bushel of 

 the dressed grain ; and, side by side with these are recorded 

 — the percentage of ash in the dry matter of the straw, the 

 percentage of silica in the ash, and the percentage of silica in 

 the dry matter. 



In the wheat in every case, and in the barley in every case Season and 

 but one, there is a higher proportion of grain in the better P roduce ' 

 season ; and in every case, of both wheat and barley, there is 

 a much higher weight per bushel of grain in the better 

 season. These conditions are, in fact, proof of the superiority 

 of the crops in the main characters of seed-forming tendency, 

 and ripening. 



The percentage of ash in the dry matter of the straw is not Season and 

 a very significant character ; and it is seen that in the case ^™ 

 of the wheat it was on the average somewhat the lower, but 

 in that of the barley uniformly the higher, in the better 

 seasons. 



The percentage of silica in the ash of the straw is more silica in 

 significant; and in both the wheat and the barley it is, ™ r hc ^ Uer 

 under all the conditions of manuring, much the lower in the of strata. 

 better seasons. More significant still is the percentage of 

 silica in the dry matter of the straw ; and it is seen that 

 with the wheat under each condition of manuring, and with 



VOL. VII. G 



