Chap. XIV. Of Change of Species. 229 



When the Quantity of Food which is fufficientfor 

 another Species (that requires lefs), but not for that 

 which Jaft grew, to grow again the next Year, then 

 that other is beneficial to be planted after it. 



The Second true Caufe is from the Conftitution of 

 Plants ; fome require more Food than others, and 

 fome are of a frronger Make, and better able to pe- 

 netrate the Earth, and forage for themfelves. 



Therefore Oats may fucceed a Crop of Wheat on 

 flrong Land, with once plowing, when Barley will 

 not* becaufe Barley is not fo well able to penetrate as 

 Oats, or Beans, or Peafe, are. 



So a Pear-tree may fucceed a Plum-tree, when 

 another Plum-tree cannot •, becaufe a Pear is a much 

 flronger Tree, and grows to a much greater Bulk ; fo 

 inclined to be a Giant, that 'tis hard to make it a 

 Dwarf; and will penetrate and force its Way thro* 

 the untill'd Earth, where the other cannot ; being of 

 a weaker and lefs robuft Conftitution, not fo well able 

 to fhift for itfelf. 



The Pear could penetrate Pores, that the other 

 could not. Mr. Evelyn fays, in his Difcourfe of 

 Foreft-trees, * That a Pear will ftrike Root thro* the 

 1 roughed and moil impenetrable Rocks and Clifts 



* of Stone itfelf.* He fays likewife, in his Pomona, 



* That Pears will thrive where neither Apple or other 



* Fruit could in Appearance be expected.' 



I can fcarce think, that a large Plant takes in 

 larger Particles than a fmall one, for its Nourifhment : 

 If it did, I can't believe, that the Thyme could 

 have ftarv'd the Apricot-tree; it muft have left the 

 larger Particles of Food for that Tree, which pro- 

 bably would have fufficed to keep it alive : I rather 

 think, that great and fmail Plants are fuftain'd by 

 the fame minute Particles ; for, as the fine Particles 

 of Oats will nourifh an Ox, fo they will nourifh a 

 Tom- tit, or a Mite. 



Q^ 3 Sonae 



