PHENOMENA OF PLANT-LIFE. 53 



the thirteenth of May, the extreme variation being 52.36 feet 

 of water. After the development of the buds, the upper gauge 

 stood uniformly at from -1 to -4 feet of water, and the lower 

 one was mostly minus. 



The bleeding of a broken grape vine, in 1720, induced the 

 Rev. Stephen Hales, an ingenious observer of nature, to at- 

 tach mercurial manometers to the stumps of vine branches 

 and stems, by means of which he obtained a maximum press- 

 ure of forty-three feet of water. These experiments were 

 made on vines of the species Vitis vim/era, in the compara- 

 tively cool and moist climate of England. It is, therefore, 

 not surprising, that the more vigorous Vitis cestivatis, 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 tpe College 

 estate were selected and prepared for observation^ The 

 smaller one was about three inches in diameter at th& 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 piece of stout rubber hose, which was con- 

 nected by means of a stopcock to the lead pipe of a mercu- 

 rial gauge. This was on May-day. The tissues of the root, 

 which had not yet awakened from its winter 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 in- 

 creased 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 



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