CHAP, xvii S Y L V A 1 47 



all) of the sap ascends by the lignous part of trees, 

 not the cortical ; nor between the cortical and lignous : 

 And that the increase of a tree's growth in thickness, 

 is by the descent of the sap, and not by the ascent ; 

 so as if there were no descent, the tree would increase 

 very little, if at all ; for that there is a perpetual 

 circulation of the sap, during the whole Summer ; 

 and whilst it is in this course, and not a descent at 

 Michaelmas only, as some hold, but evaporated by 

 the branches, during Summer and Autumn, and at 

 Spring supplied with rains. He also thinks it prob- 

 able, that the bodies of plants, as well as those of 

 animals, are nourish'd and increas'd by a double pab- 

 ulum or food ; as water and air both impregnated, 

 mixing and coalescing by a mutual conversion. 



That all plants and animals seem to have a two-fold 

 kind of roots, one spreading into the earth, the other 

 shooting up into the air ; which, as they receive and 

 carry up their proper nutriments to the body of the 

 plant and root, so they carry off the useless dregs and 

 recrements, Gfc. But this curious note seeming fitter 

 to have been plac'd in our chapter of Pruning, (upon 

 which this learned gentleman has given us his experi- 

 ence) I beg pardon for this diverticle, and return to 

 my subject. 



4. But whilst the second edition was under my 

 hand, there came to me divers papers upon this sub- 

 ject, experimentally made by a worthy friend of mine, 

 a learned and most industrious person, which I had 

 here once resolv'd to have publish'd, according to the 

 generous liberty granted me for so doing ; but under- 

 standing he was still in pursuit of that useful, and 

 curious secret, I chang'd my resolution into an earnest 

 address, that he would communicate it to the world 



