OBSERVATIONS UPON THE PHENOMENA OF PLANT-LIFE. 339 



bled twenty-eight drops per minute, May thirteenth, and the beech, on the 

 tenth of May, flowed ten drops per minute, both yielding most sap in decidedly 

 warm weather, the mean temperature for the last date being above 70° F. The 

 latex of the mulberry exuded from the bark, on the ninth of April, as a trans- 

 parent fluid which soon became milky, and the white and yellow pines flowed 

 a small quantity of turpentine, apparently from both bark and wood. 



A large red maple, which was thoroughly girdled in 1873, and whose bark 

 Lad died and peeled oflF below the girdled place, was tapped above and also be- 

 low it. The result was that it bled freely from both holes on 7iiany occasions. 

 The flow, on the eighth of April, was fifty drops per minute from the upper 

 one, and one drop from the lower one, while on the eleventh of the same 

 month, it was three drops from the upjier and fourteen drops from the lower 

 one. 



After the usual run of sap for the season has ceased, some species will bleed 

 from the stump, if cut down, just like miuiy herbaceous plants. Thus, Mr. 

 Wm. F. Flint reports that large trees of the black, yellow, and paper birch, 

 when felled on the thirtieth of June last, did not bleed immediately, as in 

 April, but after an hour or two began to exude sap freely. 



On August twenty-eighth, twenty-four species of young trees were cut down, 

 about one foot from the ground, to see whether they would bleed. None did 

 so immediately, but fifteen hours afterward the black birch ran a few drops, 

 and the following were moist on the top of the stump, viz. : alder, yellow 

 birch, red maple, cornel, ironwood, apple, elder, elm, and white pine. August 

 thirty-first, the black birch bled a little, and the yellow birch, thorn, apple, 

 glaucous willow, elm, and white pine were moist. The rest, including hem- 

 lock, shad-bush, wiiite birch, chestnut, hornbeam, beech, ash, witch-hazel, bird 

 cherry, white oak, red oak, and aspen, were perfectly dry, though all were shel- 

 tered from the sun. 



THESE RESULTS 



seem to include most of the important attainable facts in regard to the flow of 

 sap as exhibited by our common exogenous trees, and, while none of the obser- 

 vations can be exactly repeated from the nature of the phenomena, yet they 

 may safely be accepted as the substantial truth concerning the whole subject. 



WATER GAUGES. 



The interesting facts observed last year, in connection with the attachment 

 ■of mercurial gauges to the roots and trunks of trees which were known to 

 bleed from wounds, and the suggestions derived from them, were a powerful 

 stimulus to further investigations in this direction. Accordingly, a large 

 number of gauges were prepared in early spring, and, as soon as the weather 

 was suitable, attached to such trees and roots as gave promise of the most 

 valuable results. 



There still remained the unaccountable fact that the larger number of trees 

 and shrubs did not show any tendency to bleed in spring, and therefore could 

 not be made to answer any inquiries put to them in regard to the circulation 

 of sap. It was thought best to adopt a cheaper and simpler form of gauge for 

 application to such species as gave small promise of useful results. For this 

 purpose, the following economical apparatus was devised and applied to the 

 roots of elm, ash, white oak, chestnut, apple, sugar maple, and hickory. A 

 straight glass tube, three feet in length, with a bore about one quarter of an 

 inch in diameter, was joined by a conical rubber connector with each of the 



42 



