OF I^OREST-TREES. 



125 



dexterously separated from the mother-roots, and transplanted in con- CHAP. Vll. 

 venient places for propagation, as the season requires. 



Here note. That stocks raised from suckers, and employed in graffing 

 fruit, are more disposed to produce suckers, than such as come from 

 stones and pippins. 



" 5616, 2276.1. The velocities in the surface of the leaves, roots, and transverse cut of the 

 " stem, are gained by a reciprocal proportion of the surfaces. 



r leaves = 56l6 

 "Area of < roots = 2276 

 stem = 1 



velocity 



= ?Bis r lih inch. 



= or as inch. 



(. J 34, inch. 



" Now, their perspiring 34 cubic inches in twelve hours' day, there must so much 

 " pass through the stem in that time ; and the velocity would be at the rate of 34 inches 

 " in twelve hours, if the stem were quite hollow. In order, therefore, to find out the quan- 

 " tity of solid matter in the stem, July 27, at 7 a- m. I cut up even with the ground a Sun- 

 " flower ; it weighed 3 pounds ; in thirty days it was very dry, and had wasted in all, 

 " 2 pounds 4 ounces ; that is, | of its whole weight ; so here is a fourth part left for solid 

 " parts in the stem, (by throwing a piece of green sun-flower stem into water, I found it 

 " very near of the same specific gravity with water,) which filling up so much of the stem, 



the velocity of the sap must be increased proportionably, viz. | part more, (by reason of 

 " the reciprocal proportion,) that 34 cubic inches may pass the stem in twelve hours ; 

 " whence its velocity in the stem will be 45J inches in 12 hours, supposing there be no 

 " circulation nor return of the sap downwards. If there be added to 34, (which is the 

 "least velocity,) J of it = 11 J, this gives the greatest velocity, viz. 451. The spaces being 

 " as 3; 4, the velocities will be 4 ; 3 .* : 45 J : 34. But if we suppose the pores in the sur- 

 " face of the leaves to bear the same proportion as the area of the sap-vessels in the stem 

 " do to the area of the stem ; then the velocity both in the leaves, root, and stem, will be 

 "increased in the same proportion. A pretty exact account having been taken of the 

 " weight, size, and surface of this plant, and of the quantities it has imbibed and per- 

 " spired, it may not be improper here to enter into a comparison of what is taken in and 

 " perspired by a human body, and this plant. The weight of a well-sized man is equal 

 "to 160 pounds: the weight of the sun-flower is 3 pounds; so their weights are to 

 "each other as I60 : 3, or as 53 .* 1. The surface of such human body is equal to 

 "15 square feet, or 21 60 square inches. The surface of a sun-flower is 56\6 square 

 "inches; so its surface is, to the surface of a human body, as 26 10. The quantity per- 

 " spired by a man in twenty-four hours is about 31 ounces, as Dr. Keill found. Vid. 

 " Medic. Stat. Brilan. p. 14. The quantity perspired by the plant, in the same time, is 

 " 22 ounces, allowing two ounces for the perspiration of the beginning and ending of the 

 " night in July, viz. after evening, and before morning weighing, just before and after 

 "night. So the perspiration of a man to the sun-flower is as 141 ; 100. Abating the six 



Volume II. R 



