138 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



not frozen, until by accident or design some portion of the grains of the 

 wood is severed, when as is known, the sap flows ?" 



" If it docs not remain stationary, does it have a continuous flow up and 

 down the trunk of the tree?" 



" If so, then by what power, and where does it go up, and where down 

 the tree T' 



" In that species of wood known as the ' sugar maple ' is what is called 

 the ' sugar water ' really the sap of the tree ? and is it, or is it not (Essen- 

 tial to the life and growth of the tree ?" 



" What produces the saccharine quality of the ' sugar water ?" 



"It is well known that for good sugar weather it needs freezing nights 

 and thawing days. Now is it the freezing that makes the 'sugar water?' 

 And is the moisture wliich is required for its production taken into the tree 

 through the foliage and branches, or through the roots ?" 



Mr. Geo. Bartlett, from the committee appointed at the last meeting, 

 made the following very satisfactory report: 



The several queries in that communication constitute a request for a 

 general account of the circulation of sap in trees, and the formation of 

 maple sugar. We proceed to give such an account in the briefest and 

 clearest manner at our command. 



Trees are made up of fine tubes which extend from the root to the leaf, 

 and it is through these tubes that the circulation of the sap is carried on. 

 If a growing tree is pulled up by the roots, and the roots are placed in a 

 vessel of water containing some colored solution which they will absorb, 

 we can trace the course of this solutitm througli the tree by cutting notches 

 into it at successive periods. The coloring matter is always found first in 

 the bod}' of tlie wood near the root, then in the wood higher up, and so on 

 till it reaches the leaf; then it begins to appear in the inner bark near the 

 leaf, and it passes down through the bark again to the root. This obser- 

 vation shows that the circulation of the sap is up through the wood, and • 

 down through the bark. 



We are not able to answer the question of j'our correspondent, what is 

 the force that causes the sap of plants to circulate. There has been much 

 speculation in relation to it, but it has never been settled by observation 

 and experiment. It is pretty well established that sap circulates in the 

 winter, though less rapidly than in the summer, and less rapidly at that 

 time in deciduous than in evergreen trees. 



The Formation of Sugar in the Maple. 



The solid portions of thoroughly dried wood, and other parts of plants, 

 are composed mainly of water and charcoal. When charcoal is burned, a 

 small portion of ash is left. This ash is the mineral or inorganic portion 

 of the substance of the tree, and consists principally of potash, lime and 

 flint of silex. That portion which burns in carbon. In burning, the car- 

 bon unites with oxygen to form carbonic acid, an invisible gas that floats 

 away in the atmospheif. 



The water and the inorganic matters enter the tree through tlie roots; 

 the carbon enters mostly through the leaves. Carbon forms about one-half 

 of the solid substance of the tree, and water the other half 



Water is composed of two elements, oxygen and hydrogen, in the pro 



