THE AMERICAN BOTANIST 47 



planation of the phenomena is by an Irish botanist, Henry H. 

 Dixon, who, after experimenting- with water in sealed g-lass 

 tubes has discovered that water has an unexpected tensile 

 streng-th and under proper conditions will resist considerable 

 stress tending to pull it apart. It requires, in fact, a tension 

 equal to more than 150 atmospheres to sever the columns of 

 water in the ducts of plants. Dixon assumes that the evapora- 

 tion of water from the leaves sets up a pull of sufficient 

 strength to hold the water suspended in the conducting tracts 

 of even the tallest trees. In elaborating his theory he shows 

 how perfectly adapted to this function the tracheids and other 

 vessels are. Even the partitions across the ducts, which in 

 connection with any theory concerning root pressure and capil- 

 lariety would only be in the way, by the new theory are shown 

 to be an excellent contrivance for facilitating the ascent of sap. 



Natural History of Selborne. — Somewhat more than 

 a hundred years ago, there died in the southern part of Eng- 

 land an obscure country parson, Gilbert White, whose name, 

 practically unknown to his own generation, has grown great 

 with the years and is now familiar wherever an interest in 

 natural history prevails. During a long and uneventful life he 

 methodically attended to the duties of his parish and in his 

 leisure hours diligently applied himself to the study of the 

 plants and animals in the vicinity. For many years he wrote 

 letters upon the subjects of his investigations to Thomas Pen- 

 nant and Daines Barrington and these collected and published 

 in book form a few years before the writer's death formed the 

 famous "Natural History of Selborne." The regard in which 

 the book has been held in England, accounts for the fact that 

 the most important society for the study of Nature in that 

 country — a society numbering some thousands of members — 

 is called the Selborne Society. At the recent annual meeting 

 of this society, nearly a hundred different editions of the 

 famous book were shown and this by no means comprises all 

 the forms in which the work has been issued. 



