Chap. V. Of Tillage. 41 



For fibrous Roots (which alone maintain the Plant ; 

 the other Roots ferve for receiving the Chyle from 

 them, and convey it to the Stem) can take in no Nou- 

 rifhment from any Cavity, unlefs they come into 

 Contact with (V), and prefs againft, all the Superficies 

 of that Cavity, which includes them •, for it difpenfes 

 the Food to their Lacleals by fuch PrefTure only: But 

 a fibrous Root is not fo prefs'd by the Superficies of 

 a Cavity whofe Diameter is greater than that of the 

 Root. 



The Surfaces of great Clods form Declivities on 

 every Side of them, and large Cavities, which are as 

 Sinks to convey, what Rain and Dew bring, too quick- 

 ly downwards to below the plow'd Part. 



The firft and fecond Plowings with common 

 Ploughs fcarce deferve the Name of Tillage ; they 

 rather ferve to prepare the Land for Tillage. 



The third, fourth, and every fubfequent Plow- 

 ing, may be of more Benefit, and lefs Expence, than 

 any of the preceding ones. 



(e) Roots cannot have any Nourifhment from Cavities of the 

 Earth that are too large to prefs againft them, except what Water, 

 when 'tis in great Quantity, brings to them, which is imbibed by 

 the gentle PrefTure of the Water ; but when the Water is gone, 

 thofe large Cavities being empty, the PrefTure ceafes ; and this is 

 the Reafon, that when Land has few other but fuch large Cavities, 

 the Plant:-- in it always fufFer more by dry Weather, than in Land 

 which by Dung or Tillage has more minute and fewer large Ca- 

 vities. 



There may be fome Moiflure on the Superficies of large Cavi- 

 ties; but without Preffure the fibrous Roots cannot reach it ; and 

 very little or no PrefTure can be made to one Part of the Root's 

 Superficies, unlefs the Whole that is included be prefTed. 



If it be objected that a Charlock-Plant, when pulled up, and 

 thrown upon the Ground, vyill grow thereon ; this proves nothing 

 againft the Neceflity of PrefTure, &c. for theWeight of that Plant 

 prefTes fome of its Roots fo clofely againft the Ground, that they 

 fend out (unlefs the Weather be very dry) new Fibres into the 

 Earth ; and there they are prefTed in all their Superficies ; without 

 which Fibres the Plant doth not grow. 



But 



