igg BOARD OF AGRICULTURE. 



and if you carry it off you carry away those manurial matters ; what- 

 ever you leave restores what it took to make it, and no more ? 

 Prof. Johnson. Yes. 



Mr. Gould. Ought it not to be said that in its previous condi- 

 tion the manurial matter was in an insoluble condition, not adapted 

 to the plant; whereas, what you leave is in a soluble condition, 

 and assimilable ? 



Prof. Johnson. During the growth of a crop, plant-food in the 

 soil does pass from au insoluble into a soluble form, and being 

 taken up by the crop remains in that part of the crop left in the 

 field in a state adapted for immediate use. The deep rooted 

 clover also, in this case, brings up, from an average depth of 

 sixteen inches, matter which remains in part within the range of 

 shorter-rooted grain crops. 



SECOND LECTURE. 

 I was speaking yesterday on the peculiarities of plants which 

 enable them to act differently on the stores of nutriment which 

 may be supplied to them in the soil. I spoke of the differences in 

 the absolute quantity of roots which various plants put out into 

 the soil and also of the differences in the depth of roots ; and gave 

 some illustrations on those points. I propose to speak this morn- 

 ing of the different structure of the foliage of plants. 



We know with absolute certainty that a large share of the feed- 

 ing of the plant is done through the leaves. We cannot certainly 

 tell how much goes on through the leaves and how much through the 

 roots, in highly manured and very rich soil, but experiments have 

 demonstrated ''that all the carbon of the plant (which is about fifty 

 per cent, of the weight of the dry plant) may come from the 

 atmosphere ; it is not necessary that any of it should come from 

 the soil. The seeds of various agricultural plants — Indian corn, 

 oats, barley, etc.— have yielded a larger increase under artificial 

 circumstances, where the roots had no carbon whatever at their 

 disposal, than is ever produced under field culture. It is a well 

 known fact of agricultural practice, that soils which are nearly 

 destitute of vegetable matter, and therefore have no considerable 

 source of carbon in them, will produce large crops. Some very 

 sandy soils, containing but little carbon, may be made to produce 

 heavy crops by irrigation. Crops are also raised on soils free 

 from organic matter, or from sources of carbon, by the aid of 

 fertilizers which themselves furnish nothing of that sort. Carbon, 

 then, which makes up half of the weight of the dry plant, ia 



