Objects 'lo be Accomplished by Plowing. 145 



a plant have a hard, impervious soil on their right and a porous 

 soil on their left, the roots will all be directed from the right to 

 the left. The growth of roots takes place by the addition of new 

 cells to their outer extremities. The newly added cell must 

 therefore push the earth before it by a force somewhat greater 

 than the cohesive force of the soil which it penetrates. The force 

 required for this purpose exhausts the vital force of the plant. A 

 thoroughly porous soil therefore relieves this exhaustion and 

 economizes the vital force which is then directed to some other 

 point. Plants differ greatly in their power of forcing their roots 

 into the soil. Wheat and barley both radicate feebly and will 

 hardly enter a stiff soil, while buckwheat will penetrate it readily. 

 The roots of quack grass {triticum repens) will force their way 

 triumphantly through the stiffest clays, while the feebler roots of 

 timothy [p/tleum pratense) will scarcely penetrate them at all. 



Jethro TuU, to whom practical husbandry is so much indebted, 

 ascertained the range of porous land required by each kind of 

 plant in the following manner: 



In the midst of hard, impervious land he dug a trench twenty 

 yards long, in the form of a truncated wedge, the transverse 

 width of the narrow end being two feet, and the broad end being 

 twelve feet wide. In the fine, loose earth of this trapezoid he 

 planted along the middle line, at distances of one yard apart, the 

 plants whose root range he desired to ascertain. The plant one 

 yard from the narrow end was smaller than that which was two 

 yards from it, and this latter was smaller than that which was 

 three yards distant. When he found the point where the plants 

 ceased to enlarge and remained of the same size until that which 

 was nearest to the widest end, he believed that he had the meas- 

 ure of the normal length of the root of that plant; thus when 

 the trapezoid was planted with turnips each turnip was larger as 

 it receded from the narrow end until the fifteenth, from thence to 

 the twentieth the turnips were of equal size. Measuring laterally 

 from the fifteenth turnip, he found that the range of loose soil 

 was four feet, which he therefore concluded was the natural length 

 of the turnip root. 



When the first settlers of Ohio began to cultivate the rich 

 valley of the Scioto, they subjected it to a very imperfect and 

 .shallow cultivation; two or three inches was the utmost depth of 

 the plowing, but such was the great natural fertility of the land 

 ^^hat the ci'ops of Indian corn averaged seventy bushels to the acre. 

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