TRANSACTIONS OF SECTION B. 



555 



Baeeen Soils showing the peoportion of Lime and Magnesia in 1000 



PAETS of soil. 



No. 11. Refers to a soil which Dr. Sendtner characterises as the most sterile 

 soil in Bavaria. 



Nos. 12 and 13. Soils from the neighbourhood of Friesland, also barren. 



No. 14. A very barren soil from Luneberg. This soil is wanting in many- 

 other elements besides magnesia, and is probably too rich in iron. 



No. 15. Also from Luneberg, analysed by Sprengel, as also was the case with 

 the three preceding numbers. Here again I deprecate the supposition that T hold 

 the barrenness of these soils to be solely, or even principally, due to the absence or 

 scarcity of magnesia. Many of the other constituents of plants, not considered by 

 Ville as essential to a manure, are also wanting, as well as some that he deemed to 

 be indispensable. 



Probably the opinion of Dr. Liebig may carry with it more weight with the 

 generality of persons than any of the foregoing evidence in favour of making a 

 more extended use of magnesia in manures. In his ' Natural Laws of Husbandry' 

 (pp. 257-8), he says, with reference to guano, the best probably of manures now in 

 the market : ' If we compare the composition of the ashes of various seeds we at 

 once see that the incombustible constituents of guano do not altogether replace the 

 soil constantly carried off in the seeds.' 



* In 100 parts of seed-ash are contained : 



' The principal diiierence between the ash of guano and that of those seeds lies 

 in the deficiency of potash and magnesia in the former. Agriculturists are gene- 

 rally agreed about the necessity of potash for vegetation, and that a supply is 

 required by fields poor in that ingredient, or drained of it ; but the question as to 

 the importance of magnesia for seed-formation has not, as yet, met with the same 

 attention, and special experiments in this direction would be very desirable. 



' The fact that much more magnesia is found in the seeds than in the straw 

 unmistakably shows that it must play a definite part in the formation of the seed, 

 whicli might, perhaps, be ascertained by a careful examination of seeds of the 

 same variety of plants containing different amounts of magnesia. It is a well- 

 known fact that the seeds of the several species of cereals, having the same pro- 

 portion of nitrogen, do not always contain the same nitrogenous compoimds, and it 

 is possible that the natui-e of the latter may, in the formation of the seeds, be 

 essentially influenced by the presence of lime or of magnesia, so that the diSerence 

 in the proportion of both of their alkaline earths may have a certain connection with 

 the presence of the soluble nitrogenous compounds (albumen and casein), or of the 

 insoluble gluten or vegetable fibrine.' 



