PHENOMENA OF PLANT-LIFE. 59 



ing vine, which may account for the fact that the flow of crude 

 sap from the grape does not perceptibly affect its subsequent 

 growth or productiveness. 



The sap of the sugar maple contains from two to three per 

 cent, of cane sugar, while that of the red maple yields only 

 about half as much. The sap of the latter is said by Mr. H. 

 M. Sessions, of Wilbraham, also to contain some ingredient 

 which attacks iron, forming a very dark-colored syrup when 

 evaporated in pans of that metal. It is, therefore, better to 

 exclude it from the sap gathered for the manufacture of 

 sugar. 



In order to obtain as much information as possible in regard 

 to the sap of the sugar maple, an analysis was made of the 

 gas contained in the tree when first tapped. This was pro- 

 cured by inserting a stopcock into the sap-wood of a tree 

 twenty feet from the ground. To the stopcock was attached a 

 glass tube by means of a rubber connector and the tube passed 

 through a cork into a large bottle, reaching to the bottom. 

 As soon as the bottle was filled with sap, it was tightly closed 

 and taken to the laboratory, where the gas was separated by 

 boiling. The analysis shows that the gas contains much less 

 nitrogen and more oxygen than atmospheric air, while the 

 proportion of carbonic acid gas is about one hundred and 

 thirty-four times greater in the former than in the latter. 



As we do not know how or when the cane sugar is formed 

 in the mnple, we cannot account for the variations in the 

 sweetness of its sap, which are, however, very great. As 

 the flow depends upon the freezing and thawing of the wood, 

 and possibly upon the continuance of absorption by the roots 

 to supply the drain upon the tapped tree, it is evident that a 

 large body of snow upon the ground will favor it, since the 

 e;irth will then be warmer and the night temperature of the 

 air much colder than under other circumstances. It does not 

 appear that there is any greater proportion of sap in the 

 maple than in many other trees, but only that for some 

 unknown reason it is separated in greater quantity by freezing, 

 or else not reabsorbed after such separation so quickly as in 

 other species. 



For the purpose of learning whether root absorption is 

 necessary to keep up the flow of sap through the season, a 



