On the Growth of Barley hj different Manures, S^-c. 511 



the more pertinent illustrations, to quote some recent experiments, 

 in which wheat and barley were respectively grown in pots, but 

 with a very different object from that in reference to which they are 

 here cited. In these experiments the distribution of the roots of 

 the two plants was so strikingly different, that when disinterred 

 rough sketches of them were made, of which the following are 

 copies : — 



The conditions under which these plants were grown, in pots, 

 under cover, and both during the summer months, were, it is true, 

 rather artificial. Still the contrast here shown is pretty cha- 

 racteristic of the plants as grown in our fields. These outlines 

 will therefore serve to fix the mind on the bearing of the points 

 we have been discussing. It may perhaps be further explained, 

 that, whilst in the case of the barley plant only one single fibrile 

 found its way through the bottom of the pot, the wheat threw 

 out such a mass of ramifications that the whole of the surface of 

 the dish in which the pot rested was covered with a thick net- 

 work of roots ; as also was the bottom, and to a great extent the 

 sides, of the inside of the pot itself. 



Still referring to the action and province of mineral manures 

 applied to our crops grown on cultivated land, it has been sliown 

 on former occasions that, in a soil brought to what maybe termed 

 a condition of agricultural exhaustion — that is, at the end of a 

 rotation, when in the ordinary course of things it would receive 

 manure of some kind — the autumn-sown wheat was not increased 

 in produce by the direct application of mineral manures, until 

 so many crops had been taken from the land as to exhaust it of 



