170 NATURAL HISTORY OF THE FARM 



ion made through the bark, from every wound or 

 broken twig, the sap flows copiously. It flows first on 

 the south side of the tree, where the sun shines, and it 

 flows most copiously during the warmer part of the day. 

 It ceases at night when the treetop is cooled and the 

 pressure equalized. It slackens on cloudy days, and 

 ceases altogether when the ground gets warmer. The longer 

 the period of alternating bright sunshiny days and sharp 

 frosty nights, the greater the amount of sap obtainable. 

 The greater, also, is the drain of the food reserve of the 

 tree : but the provident maples store more than they need, 

 and they are not injured by the loss of such amounts as may 

 be obtained by proper tapping. They often have to meet such 

 losses through natural causes such as the tappings of the sap- 

 suckers, and the "bleeding" from the stubs of broken boughs. 

 Other deciduous woody plants lose their sap in similar 

 ways. Every vine-grower knows that grape vines, trimmed 

 at the time of abundant sap-flow, "bleed" profusely from the 

 base of every branch removed so profusely, indeed, that the 

 plant may be weakened by such inopportune treatment. Ash 

 and elm and beech and butternut and other deciduous trees 

 will yield sap in its season, but only a few of the maples yield 

 a sap that is sufficient in quantity, rich enough in sugar, and 

 sufficiently well flavored to be important to us. The sugar 

 maple is the best maple, both in yield and in quality of 

 product: a variety of it known as the black maple, is 

 especially esteemed by many growers. Red and silver 

 maples yield a copious, but more watery sap. The Oregon 

 maple is a western species from which a little sugar is made. 

 The yield of the lesser maples and of the related box-elders is 

 of no consequence. Most tree-saps, on evaporation, will 

 yield some sort of a sweetish treacle; but only the maples 

 yield palatable syrups and sugars, whose flavor is improved 

 by the non-sugary natural substances present in the sap. 



