AMHERST EXPERIMENTS ON SAP-PRESSURE. 425 



Instruction in forest-culture recommended at the State Agricultural College 

 at Amherst. 



The executive committee of tbe Massachusetts Agricultural College 

 (Amherst), iu a report made in February, 1876, included the following 

 recommendation, which, being fully discussed, was adopted: 



It is also recommended that some instruction be given in forestry, both theoretically 

 and practically, aad that special attention be paid to the raising of forest trees from 

 seed, their care and treatment in the nursery, their permanent planting in various por- 

 tions of the farm, and the subsequent care of the plantations. The time is not far dis- 

 tant when every farmer in the country will, in his owu interest, be obliged to give 

 some attention to the subject of tree-planting, and such a course as is here recom- 

 mended will be of advantage to the students and to the State at large. Similar con- 

 siderations apply to the raising of fruit-trees. A nursery of reliable standard fruit- 

 trees, adapted to one section, ought to be a source of some income to the institution. 



Experiments upon the pressure and floic of Sap, at the Massachusetts State 

 Agricultural College. 



About 1720, the Eev. Stephen Hales, an English clergyman, began 

 a series of experiments upon the pressure of sap, and the absorption 

 of water by plants, carefully weighing, measuring, and publishing the 

 results. These experiments have since been quoted by vegetable- 

 physiologists, and have formed the basis of much that is known upon 

 this subject, by leading to investigations and suggesting methods of 

 research. 



With the view of studying the laws that govern the flow of sap in 

 our American forest trees, a series of experiments was begun, in the 

 spring of 1873, at the Agricultural College at Amherst, by its president, 

 Wm. S. Clark and associates, which have led to very interesting results. 

 Several mercurial gauges were provided and attached to trees, which 

 were tapped and connected, so that the pressure of the sap could be read 

 upon a scale. Trees were tapped in great variety, and the facts noted 

 concerning the flow of sap ; but by far the most interesting results were 

 obtained upon the sugar-maple and the black birch. 



It has long been known that sap can be obtained from the sugar- 

 maple, at any time between the fall of the leaves in autumn and the near 

 approach of their return, whenever a bright warm day follows a freezing 

 night. In fact sugar has been made from the maple in every month 

 from October to May. It is also well known that the flow of sap in the 

 sugar-season depends very much upon the meteorological conditions, 

 and that the rate of flow changes in diff'erent hours of the day. The 

 temperature must be above the freezing-point, and the preceding night 

 should be below it. A bright warm day, with a west wind, following a 

 night of severe frost, the ground being abundantly moist or still covered 

 with snow, affords perhaps the best flow in the proper season. Freez- 

 ing appears indispensable, and no maple-sugar can be made where there 

 is no frost. 



In the Amherst experiments it was found that the pressure was in- 

 tvard at some hours, and outward at others. From records ruuniog 

 through two spring seasons (1873 and 1874), and from the detailed 

 results, as published by President Clark,^ we present the following : 



We found that sap flowed from the heart- wood ; that the flow was 

 regular and long continued, but not so abundant as from sap-wood, 

 and that by simply removing the bark, without wounding the wood, the 

 sap flowed profusely, but stopped early. The surface flow, where the 



^Agriculture of Massachusetts, 1873-'74, pp. 159-204, and the same for 1874-75, pp. 204- 

 312. These articles were also separately published. 



