226 ASH FROM OAT AND BARLEY STRAW ALSO VARIABLE. 



leaves very unlike quantities of ash. Thus, according to Sprengel and 

 Schrader, 100 lbs. of 



Sprengel. SchracJer. 



Oat Straw leave . 5-74 lbs. 4-42 lbs. 6-6 J. 



Barley straw . . 5-24 lbs. 8-54 lbs. 

 We cannot help conceding, therefore, generally, in regard to the cereal 

 grasses, that different varikties, at least, of the same plant, may contain 

 inorganic matter in different proportions. 



But certain analyses which have been made seem to demand a still 

 further concession. Thus De Saussure found that the ash left by the 

 same tree or shrub — by the fir or the juniper for example — differed both 

 in kind and in quantity, according as it grew uj)on a granitic or calca- 

 reous soil. Berthier also found the ash of a piece of Norway pine {pi- 

 nus abies) to differ very much from that of the wood of the same pine 

 grown in France. From these and a few other observations, the con- 

 clusion has been very generally drawn by vegetable physiologists, that 

 the ash of plants in general is determined both in kind and quantity by 

 the soil in which they grow. 



This is very likely to be true to a certain extent, as we have seen in 

 the straw of the bog oat above adverted to, but a sufficient number of 

 accurate comparative analyses of the ash of cultivated plants* has not 

 yet been published, to enable us to determine the precise influence of the 

 soil in all cases. It is impossible, however, that the prevailing charac- 

 ter of the soil can have more than a general influence on the character ot 

 the ash of any living vegetable — so long as the plant retains a healthy 

 state. The experiments of De Saussure do not appear to have been 

 made with sufficient care,f while the only comparative experiment of 

 Berthier is open to objections of another kind. 



I have said that the quantity and kind of the ash is likely to be affected 

 by the character of the soil to a certain extent. The following considera- 

 tions seem to embody nearly all the sources of such variation, of which 

 we can at present speak with any degree of certainty : — 



1°. Plants at different periods of their growth reciuire for the produc- 

 tion of their several parts, and therefore appropriate from the soil, differ- 

 ent inorganic substances ;t hence the ash will vary with the age of the 

 plant. 



• Five samples of the same variety of wheat (Hunter's wheat) grown on different soils in 

 the neighbourhood of Haddington, gave me very nearly the same proportions of ash. Thus 

 the sample grown on a 



Per cent. 

 1°. Deep reddish clay loam, subsoil gravel, left 1776 



2°. Red clay on gravel 1787 



3°. Stiff clay on retentive subsoil 1-903 



4°. Liiiht clay on rather retentive subsoil . . 1-917 



5°. Light turnip land 1-824 



These results approach very near each other. The differences are perhaps too slight to' 

 justify us in concluding that the ash is greatest in quantity when the subsoil is most reten- 

 tive. 



t The accuracy of De Saussure's analyses is rendered very doubtful by the fact that, In 

 the ash o{ ail the different trees and shrubs he examined, he found a large quantity, in that 

 of the juniper as much as 43 per cent, of alumina, and in that of the pine from 12 to 16 per 

 cent., while Berthier, whose skill is undisputed, found no alumina in the ash of any of the 

 numerous trees on which his experiments were made. 



} This fact indicates an exceedingly interesting field of chemical research in connection 

 with practical agriculture. What substance will bring this or that seed into early leaf? — 

 what will hasten its growth in middle life 1— what will bring it to ear,; maturity 1 The wheat 



