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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



formed from starch in the late winter and early spring. This starch is 

 stored in certain sapwood cells during the preceding summer, and is prob- 

 ably transformed into sugar through the action of enzymes. The starch 

 is formed in the leaves under the influence of sunlight. A large leaf area 

 and plenty of sunshine conduce to sugar-making. The reverse conditions 

 hinder it. 



2. What is the cause of the sap flow ? — The immediate cause of the 

 flow from the tap-hole is sap movement under pressure towards the point 

 of least resistance. The exciting cause of this flow seems to be tempera- 

 ture fluctuations over the 32° F. line, causing alternation of pressure and 

 suction, a pump-like action. The ultimate and absolute cause can hardly 

 be this or any other physical one. It probably is a function of the living 

 cell. 



3. What relations to the sap flow are borne by weather changes, the 

 water and gas contents of the tree, pressure and suction, and direction of 

 sap movemen t ? — The Maple trunk rapidly accumulates water during the 

 late winter and early spring. It at all times contains much gas inclosed 

 within the cell- walls of the woody tissues. The sap passes through these 

 walls readily, gas scarcely at all. Temperature changes cause expansion 

 or contraction of volume, and changes in pressure of the imprisoned gases. 

 Increase of water- content and rising temperature produce pressure, 

 pressure induces sap movement, and sap movement means sap flow. 

 Alternations of temperature above and below freezing cause alternate 

 conditions of pressure and suction, and bring about a pump-like action 

 which accounts in some measure for the intermittent flow. 



4. What bearing has location of the tree and variations in tapping on 

 the amount and character of the flow ? — Trees in the open give more and 

 richer sap than those further back in the bush, crowded and shaded, 

 because of greater leaf expansion and sun exposure. No decided 

 advantage arises from a too careful selection of any particular side for 

 tapping. The sap obtained from the customary tapping height (4 feet) 

 was found to be greater in quantity and better in quality than that 

 from the root (at ground level), or higher on the tree (14 feet above the 

 ground). 



5. What is the extent and cause of sap variation ? — 63 per cent, of 

 the sap drops before noon. Its sugar- content slightly increases as the 

 day goes on. As between orchards there are large variations — in five 

 cases 2*08 and 3*44 per cent. In the same place in consecutive years the 

 sugar- contents were 2*14 and 2*42 per cent., while the average sugar con- 

 tent in sap flowing from the experimental trees was 3*13 and 3*41 per 

 cent. 



6. What draft does an average sugar-yield make upon the total sugar- 

 content of a tree ? — Provided 3 lb. of sugar be made to the tree, from 

 4-9 per cent., according to the size of the tree, is removed. 



The average Maple-sugar crop of the United States approximates to 

 45,000,000 lb. The money value of the 1899 crop, which was below the 

 average, is placed by the census returns at $2,686,711. No Maple sugar 

 is made south of 35° latitude, or west of 95° longitude. Vermont 

 furnishes from a quarter to a third of the gross yield, from a third to 

 two-fifths of the sugar, and a tenth of the syrup. Maple sugar-making 



