Books and Current Literature. 119 



Preparation of distilled water for the atmometer. — Ordinary 

 distilled water is apt to prove injurious to the cups in time. For 

 this use the water should be as carefully prepared as for accurate 

 chemical analysis. No natural water has been found at all 

 possible for this work. Many rec:)rds have been lost through 

 attempts to use natural water. Distilled water may be trans- 

 ported in the field in heavy tin canteens, which should be cri nped 

 together, and soldered on the outside with rosin and no acid. 



Correction for absorption by rain. A new form of instrun ent 

 has been described in the Plant World, 13:79, 1910, by the use 

 of which rain-water falling upon the cup can not enter the reser- 

 voir, thus removing one of the greatest objections to the porous 

 cup as an ecological instrument in humid regions. 

 The Johns Hopkins University, 



Mar. 2, 1910. 



BOOKS AND CURRENT LITERATURE. 



Scharfetter, in the Austrian botanical Zeitschrift, discusses 

 the poverty of species, especially Alpine species, of the eastern 

 extensions of the central Alps, which is attributed to the follow- 

 ing causes: 1. The uniformity of the geological substratum. 

 2. The limited extent of the areas lying above tree line. 3. The 

 limited variety of habitats. 4. The close associations which 

 have covered the ground since the Glacial epoch and have been a 

 hindrance to the entrance and establishment of outside species. 



Engler's Contributions to the Flora of Africa, XXXV, 1909, 

 includes an instructive account of the discovery of a representa- 

 tive of the Triuridaceae in West Africa and the geographical 

 relations inferred therefrom. The seeds of these saprophvtic 

 plants are quite incapable of distribution by ocean currents, 

 and the family is therefore to be regarded as of great age, ex- 

 tending back to the Tertiary, beyond the time of the first occu- 

 pation of the continents by the rain forest, and to a time when 

 the Seychelles, where this family is still represented, was con- 

 nected more closely with the main land, 



