250 BOARD OF AGRICULTURE. 



ured in a similar way, with the omission of the sign. Thirty- 

 six inches of water in one of these tubes weighed one ounce, 

 and from these data it was easy to learn the actual amount of 

 water which was taken up or thrown off daily by each species. 

 The table of observations for six common trees, which is ap- 

 pended, will convey a correct impression of the peculiarities 

 of this phenomenon. 



One of the most remarkable discoveries, in this connection, 

 is the entirely unexpected fact that the roots of the sugar 

 maple do not exude any sap from their wood when protected 

 from frost, and show less independent power of absorbing 

 water from the soil than almost any other species. Hence, 

 there was no flow from the root into the tube at any time, 

 but a constant moderate absorption of water from it. 



The flow from the root into the tube is similar to that 

 observed in the tube of an ordinary osmometer ; but this does 

 not prove that osmose has any influence in this matter, and 

 the doubt about it is not diminished when we see the water 

 moving, sometimes in one direction and sometimes in another. 

 In the sugar maple, the flow was always out of the tube into 

 the wood of the root ; in the white oak, the absorption from 

 the tube was, in some cases, as much as one ounce in thirty 

 minutes, but rarely the current was reversed and absorption 

 occurred from the ground ; while, in the elm, the absorption 

 from the tube was at its maximum, April fifteenth, and then 

 gradually diminished until April twenty-first, from which date 

 the flow into the tube continued till June thirtieth, when the 

 observations were suspended. 



A section of a white oak root, eight inches long and one 

 inch in diameter, which was freshly dug from the damp earth, 

 April eleventh, and weighed, was then placed with one end 

 in water three-eighths of an inch in depth, and in ten hours 

 absorbed 3.19 per cent, of its weight. This shows that the 

 tissues were far from saturated, and were in an excellent con- 

 dition to facilitate ordinary root absorption. A mercurial 

 gauge attached to a root of white oak showed on the twelfth 

 of April a suction sufficient to sustain a column of water 10.20 

 feet in height, which was caused by the absorption of the 

 water in the connecting tube between the gauge and the root. 



The mercurial gauge, which was used for determining the 



