No. 474] 



SAP FLOW IN MAPLE 



417 



The gas content of maple wood was found by the Vermont 

 workers to be about 24 of the volume of the wood. This gas 

 consists largely of oxygen, carbon dioxide, and nitrogen, which 

 are either produced by metabolism or have passed in from the air. 



During the late winter of 1904 I made a number of observations 

 concerning the disposition of the gas in the wood of a number 

 of trees, and the results may here be added. Sections were made 

 with a razor either under water or under oil, and mounted in the 

 medium in which cut. Looking quickly through the microscope 

 before changes could occur, the disposition of the bubbles of gas 

 could be quite readily ascertained. It was found that in the maples 

 the vessels contained relatively little gas, sometimes appearing 

 saturated with sap, while the wood fibers usually contained a large 

 quantity of gas. In some cases the latter were nearly filled with 

 gas, in others only a part of them filled, and in a few specimens 

 of sugar maple T could find no gas in any part of the section. 

 Nyssa and (,'ladrastis showed little gas in the vessels during the 

 bleeding season, and little in the fibers. Juglans showed little in 

 the very large vessels while the fibers seemed always to be filled 

 with gas. The other trees examined showed more gas tlian sap 

 in the vessels. 



The following table gives the results in detail: — 



gas in wood fibers. 



Acer saccharum. No gas in inner vessels, possibly a bubble in outer; 

 gas in fibers. Bled in room. 



