PHENOMENA OF PLANT-LIFE. 63 



An important and elegant demonstration of this theory was 

 obtained by cutting large branches, fifteen to twenty feet in 

 length, when the thermometer was below zero, from trees of 

 the sugar maple, white birch, elm, hickory, button wood, 

 chestnut and willow, and suspending them in the warm air of 

 the Durfee Plant-House. The maple soon began to bleed at 

 the rate of twenty-four drops per minute, while the button- 

 wood bled eleven drops, and the hickory exuded a little very 

 sweet sap, precisely as in spring. The birch, elm, chestnut* 

 and willow did not flow at all, and were not even moist on 

 the freshly-cut surface. 



A mercurial gauge, attached to the end of a frozen branch 

 of sugar maple, indicated pressure and suction when the tem- 

 perature was raised ancl lowered, precisely as it would have 

 done upon a maple tree during the ordinary alternations of 

 day and night in the spring of the year when the sap is 

 flowing. 



In the warm regions of Asia, Africa and America, are found 

 about one thousand species of palm trees, from many of 

 which a sweet sap is obtained in large quantities. This is 

 simply allowed to ferment, and drank as palm-wine or toddy, 

 or distilled for the production of a sort of brandy, or it is 

 evaporated for the extraction of its sugar in the form of syrup, 

 or of a more or less crystalline solid called jaggery. In the 

 province of Bengal, in India, more than one hundred million 

 pounds of palm-sugar are manufactured annually, while the 

 total product of palm- wine in the world greatly exceeds that 

 of wine from the grape. 



There are three principal methods adopted in different 

 countries for obtaining the sweet sap of palms. In Chili, 

 trees fifty feet high are felled in such a way that the top will 

 lie higher than the butt of the trunk, and the single terminal 

 bud with the crown of leaves is cut off". The sap flows abun- 

 dantly from the higher end of this log, and if a fresh slice of 

 wood be removed every day the bleeding continues for 

 several months. The yield is greatest during the warmest 

 days, and amounts in all to an average of ninety gallons, or 

 about seven hundred and twenty-five pounds, from each tree. 

 This sap is mostly evaporated and utilized as a very agreeable 

 syrup called palm-honey. 



