388 HORTUS GRAMINEUS WOBURNENSIS. 



careful analysis ; and the results shewed that the different vege- 

 tables so produced, contained all the constituents of the different 

 species, precisely the same as when the plants were cultivated on 

 their natural soils.* 



Some have supposed that the antipathy of plants arises from the 

 roots depositing a noxious matter in the soil. And, according to 

 the experiments of M. Burgmanns, oats are thus killed by the field 

 saw-wort; wheat by the blue erigeron; flax by the corn scabious, 

 and the purple spurge ; and buck-wheat by the corn spurry. 



The analysis of a plant, therefore, and of the soil which pro- 

 duced it, appear insufficient to account for the true cause of the 

 impoverishing principle of vegetables to the soil, and why one 

 species should exhaust it more than another. 



Some useful information, however, on this very interesting 

 point, may probably be drawn from facts obtained by daily prac- 

 tice and observation in the garden and the farm. 



Green Food. N ^ tritive - 



Ibs. Ibs. 



Mangel-wurzel, or white beet, (Beta cicla), 



produces upon a suitable soil, or a deep rich 



loam, on an average, twenty-five tons of 



green food per acre, every pound weight of 



which contains 390 grains of nutritive mat- 

 ter ; and therefore per acre 

 Carrots (Daucus carota), produce upon a deep 



light loam, on an average, eleven tons, every . 



pound of which contains 750 grains of nu- * 2 



tritive matter 

 Potatoes (Solarium tuberosum), produce upon a 



fresh loam, of intermediate quality as to 



moisture and dryness, on an average, 15 tons )> 33600 - 4800 



per acre, affording of nutritive matter per 



pound, 1000 grains 

 The common field or white turnip (Brassica \ 



rapa, var.) affords from a sandy loam, upon / 



an average, per acre, 16 tons of green food, S 35840 - 1638 



a pound of which contains 320 grains of nu- t 



- J 



tritive matter 



* Annales de Chimie, Fev. et Mars, 1808. 



