68 THE VEGETATIVE FUNCTIONS OF PLANTS 
thawing and freezing. During this season, in many parts 
of the country, it is customary to "tap" the trees, by 
boring a small hole into the trunk far enough to enter the 
wood, and then insert a wooden or metal "spiggot" or 
spout, through which the sap flows out and is caught in 
pails. It is then "boiled down," either in the sugar bush 
or in the house, until the water has passed off in large 
quantities as steam, leaving a thickened maple syrup in 
the kettle or evaporating pan. If the boiling is continued 
the syrup, when cooled, becomes maple sugar. The saps 
of the sugar-cane and of the sugar-beet are, as is well 
known, the source of the ordinary sugars of commerce. 
