310 STATE POMOLOGICAL SOCIETY. 



that roots containing sugar do not exude it when growing in water, while 

 leaves and fruits when immersed in this fluid, readil}' absorb it by an osmotic 

 process and part with their sugar. If the enormous absorption of water by the 

 roots of birch trees, in spring, were accompanied by any corresponding exuda- 

 tion, it would appear easy to find it; but no one has yet detected it. It is not 

 possible to account for the fact that when sap is rising most rapidly, none will 

 flow from a wound in the bark, even when it will run a stream from the outer 

 layer of wood, if the circulation in the trunk is caused by osmose. There is 

 fresh cellular tissue in the liber, and some soluble material, but the bark 

 remains comparatively dry till growth begins. After the cambium has become 

 abundant, why should not all the crude sap press toward it and draw the 

 elaborated material directly into the wood, instead of pushing its way against 

 the force of gravity to the leaves, if osmose is so powerful an agent in the cir- 

 culation ? If this tendency to press into the bark were to exist, there would be 

 a much greater flow from places that are girdled than is now observed; and 

 probably the bark itself w^ould be ruptured by the pressure exerted, which 

 would often be equal to more than thirty pounds to the square inch. 



A SURPRISING FACT. 



One of the mest surprising facts to be noticed in examining the wood of any 

 tree with well-developed foliage, is the entire absence of anything like free or 

 fluid water. A freshly-cut surface of the sap-wood is not even moist to the 

 touch; and if a tube be inserted into the trunk of such a tree, it will fre- 

 quently absorb water with great avidity. On the sixth of June last, a half- 

 inch tube six feet in length was attached to a stopcock inserted into the trunk 

 of an elm and the tube filled with water. The absorption was so rapid that 

 the fluid disappeared in thirty minutes, and this was repeated several times 

 the same day. Similar observations were made upon white oak, chestnut and 

 buttonwood trees. 



IMBIBITION. 



Now the absorption was not osmotic, since the rapidity of it was too great 

 and there was no outward flow, buc apparently the result of imbibition, or the 

 affinity of the cellulose of the woody fibre for water. Is not this, then, the 

 j-)roper name for the force which carries up the crude sap ? 



TEK CENT OF SAP. 



The wood of growing trees when cut from near the surface, though appar- 

 ently dry, contains nearly fifty per cent of water; and in the young twigs, with 

 a living pith, the proportion is even greater. A number of analyses have been 

 made of specimens collected at difierent seasons during the past year, of which 

 a tabular statement is appended. 



SAP IN THE BUDS. 



There is good reason to believe that the sap in ordinary trees begins to move 

 ■first in the buds, and that the first supply of water exhaled in the spring is 

 derived from the snp-wood. Branches of aspen and red maple, two feefc in 

 length, were cut on the twenty-sixth of March and placed in a warm room in 

 an empty vase. The flower-buds developed without any other water than what 

 they could abstract from the wood, so that on the filth day the staminate cat- 

 kins of the aspen were four inches long, and the pollen well developed. It is 

 -by no means uncommon to see large branches, which have been removed from 



