OBSERVATIONS UPON THE PHENOMENA OF PLANT-LIFE. 335 



branches and stems, by means of which he obtained a maximum pressure of 

 forty-three feet of water. These experiments were made on vines of the species 

 Viiis vinifera, in the comparatively cool and moist climate of England. It is, 

 therefore, not surprising, that the more vigorous Vilis mstivalis, in the more 

 fervid and sunny climate of Massachusetts, should exert a greatly superior 

 force. In order to determine as many facts as possible concerning the flow 

 and pressure of the sap of the wild summer grape, two of the largest vines on 

 the College estate were selected and prepared for observation. The smaller 

 one was about three inches in diameter at the ground, and spread over a young 

 elm, some forty feet in height, and standing in moist, open land. One of the 

 main roots of the vine was uncovered and followed from the stem toward its 

 extremities, a distance of four feet, where it was cut off. To the large end of 

 this detached root, the remainder of which was left undisturbed in the soil as 

 it grew, was firmly fastened a stout piece of rubber hose, which was connected 

 by means of a stopcock to the lead pipe of a mercurial gauge. This was on 

 May-day. The tissues of the root, which had not yet awakened from its win- 

 ter sleep, at once began to absorb the water from the gauge, and the next day 

 there appeared a suction equal to -4.53 feet of water. This continued, though 

 gradually diminishing, till it reached zero, on the tenth of May. From this 

 time the pressure still increased until, on the twenty-ninth of the month, it 

 became sufficient to sustain a column of water 88.74 feet in height, which is 

 more than twice as great as the maximum observed by Hales, and the greatest 

 pressure ever produced by the sap of a plant so far as we know. It is an 

 interesting fact that this maximum occurred on the warmest day in May, the 

 mean temperature having been 71.7*^ F. It is also noteworthy that, on the 

 very day when the gauge first showed pressure, the vine which was tapped 

 began to flow, though it was half a mile distant. The pressure on the gauge 

 steadily dimished through the season, and, on the fourteenth of September, 

 amounted to 19.35 feet. The extreme variation was 93.27 feet of water, and, 

 therefore, 9.41 feet less than in the case of the black birch root, which exhib- 

 ited a much greater suction, though less pressure, than the grape root. 



The other vine selected for trial was nearly four inches in diameter and 

 more than fifty feet high. To a large branch of this, near the ground, was 

 attached a gauge by means of a rubber hose, the branch being cut oS" for that 

 purpose. A second gauge was secured to another branch at the height of 

 thirty feet above the first, and observations made upon them once, twice, or 

 three times, dail}^, from May seventh to June thirtieth. After this, occasional 

 visits were made to the vine, though the variations were very slight. The 

 pressure on the lower gauge began on the seventh of May, when it was 11.11 

 feet of water, and reached its maximum on the twenty-sixth day of the month, 

 equalling a column of water 83.87 feet in height. The pressure declined quite 

 rapidly as soon as the buds began to develop, and fell to zero June thirteenth. 

 The greatest suction w^as exhibited on the twenty-ninth of June, and was 

 equal to sustaining a column of water 14.39 feet high. Daring the month of 

 July, when growth was most rapid, the suction was uniformly about -7.37 

 feet of water, and during August about -4 feet. The extreme variation on 

 this gauge amounted to 98.26 feet, though the pressure was somewhat less than 

 was shown by that on the detached root of the vine already mentioned. 



The upper gauge was not reached by the sap rising from the root until some 

 days after pressure was manifest at the lower one. On the twelfth of May the 

 lower one stood at 34.11 feet of water, and the upper at 3.40 feet. The maxi- 



