SPKING FLOW OF SAP. 163 



at some results which seem to be new and important. The 

 amount of mental and manual labor involved in such investi- 

 gations, even after a statement of the facts, can hardly be 

 appreciated, except by those who have been engaged in similar 

 work. 



The task of making, adjusting and repairing six mercurial 

 gauges used in determining the pressure exerted by the sap 

 of different trees, and the recording of most of the observa- 

 tions, was cheerfully undertaken and most faithfully performed 

 by Prof. S. H. Peabocly, who also prepared with great skill 

 a chart representing upon a uniform scale the results of all 

 the observations. He visited every gauge under his charge 

 from three to six times every twenty-four houi's for several 

 weeks. All of them were necessarily at considerable distance 

 from his residence, and one Avas reached by a perpendicular 

 ladder forty-two feet in height, so that taking observations, 

 • especially in dark and stormy nights, was far from a pastime. 



Prof. Levi Stockbrido:e recorded with o-reat care and inter- 

 est the fluctuations in the mercury in the gauge upon the 

 sugar-maple during a period of ninety days. 



Prof. C. A. Goessmann took the specific gravity of a large 

 number of specimens of sap from many species of trees, and 

 from the same trees at different times, and applied chemical 

 tests for the determination of susfar and other ino:redients. 



Mr. Albert T. Wakefield, of the senior class, devoted 

 much time for some weeks to tapping the various trees of the 

 forest, collecting specimens of sap for analysis, and weighing 

 the daily flow from the several trees under observation. As 

 these were widely scattered over the College estate, their vis- 

 itation necessitated a somewhat extended journey at a season 

 when people generally do not walk the fields for pleasure. 



When it is further added that over sixty species of trees 

 and shrubs were tapped, most of them several times, and 

 that the extreme points where observations were made were 

 more than five miles apart, some conception may be attained 

 of the labor required for the acquisition of these few facts. 



In order that the results of our investigations may be more 

 fully appreciated, and the questions involved more clearly ap- 

 prehended, it seems necessq,ry to discuss briefly the general 

 structure of plants and the numerous theories which have 



