222 BOOKS AND CURRENT LITERATURE 



Harshberger, in discussing the same matter, states that accuracy in 

 specific determinations is highly to be desired, but continues "vegeta- 

 tion can be described without mentioning specifically a single plant." 

 No one has yet done this but it is highly desirable to keep in mind the 

 fact that in such work as Harshberger has done in Florida the names of 

 the plants are a mere convenience, like the numbering of the buoys 

 which mark a channel. It would be a notable event for some one to 

 describe the vegetation of an extended region without using the names of 

 any of the plants, for he would then be compelled to tell us a great deal 

 more about the plants, and in fact would have to work much longer be- 

 fore being ready to publish. To the navigator who depends upon the 

 numbering of the buoys the numbers are very important; to the naviga- 

 tor who takes his own soundings the numbers become superfluous. — 

 Forrest Shreve. 



The Transpiring Power of Leaves. — Physiologists and ecologists 

 will be particularly interested in BakkeV recent article on foliar trans- 

 piring power as indicated by tests with cobalt chloride paper. The 

 method used was essentially Livingston's modification of Stahl's well- 

 known cobalt chloride method of studying plant surfaces as to their 

 ability to give off water. A determination is made of the time required 

 for the change in color (from blue to pink) of slips of filter paper im- 

 pregnated with cobalt chloride, when they are placed over a standard 

 water-supplying surface of saturated blotting paper blanketed by a 

 millimeter of air. The time required for the same change of the same 

 slips is then determined when these are applied directly to the transpir- 

 ing plant surface, by means of small glass clips. The ratio of the 

 length of the first time to that of the second is the index of transpiring 

 power of the plant surface in question ; it is a number which expresses 

 the relative ability of the plant surface to supply water to the atmos- 

 phere, and is directly comparable with other indices similarly obtained 

 for different plants, or for the same plant at different times. It was the 

 object of the investigation here reviewed to test the method upon a 

 large number of plant species and upon different individuals of the same 

 species. The work was done at Tucson, Arizona, upon plants growing 

 mostly under irrigation. 



A detailed study of the daily march of the foliar transpiring power of 



1 Bakke, A. L., Studies on the transpiring power of plants as indicated by the 

 method of standardized hygrometic paper. The Journal of Ecology, 2:145-173. 

 1914. 



