174 BOOKS AND CURRENT LITERATURE 



ings, may render either the illuminated or the shaded side warmer than 

 the other. Which side might be warmer cannot be foretold, under 

 such conditions as are here considered, without detailed knowledge of 

 these currents. (3d) Differences in the evaporation rate from shaded 

 and lighted portions of the air-exposed surface may cause temperature 

 differences in several ways; these possibilities need not be further 

 analyzed. (4) Finally, differences in the moisture content of the cell- 

 wall, on the illuminated and shaded sides, may produce the observed 

 reactions as hydrotropic responses. The lighted side should be some- 

 what drier than the other side, whatever may be its temperature con- 

 dition. If one of two like water-imbibed surfaces receives radiant 

 energy and the other does not, it is quite possible for the former to 

 evaporate more water than the latter, even though the other conditions 

 may make the former the cooler of the two. It may be added that 

 differences in moisture content between the two sides of the cell need 

 not be postulated as a result of greater evaporation from one side; 

 the moisture content of all the portions of the cell may remain alike, 

 but the movement of water through the cell (from absorbing to trans- 

 spiring surface) may bring about chemical differences between two 

 regions of the protoplasm. 



It seems highly probable to the reviewer that the author's inter- 

 pretation is the correct one, but the experimental evidence seems to 

 be no more in its favor than in favor of any one of several other possible 

 interpretations, some of the most obvious of which have been mentioned 

 in the incomplete logical analysis that has just been outlined. There 

 is no doubt at all that these organisms do respond to one-sided illumi- 

 nation by diffused daylight, under the other conditions of Fromme's 

 experiments; whether they respond directly to the light influence has 

 not been investigated. — B. E. Livingston. 



Trent Forest Survey. — Eighty years ago the Canadian govern- 

 ment started work upon the Trent Canal, which was to provide a 

 waterway connecting Lake Ontario and Georgian Bay, and to aid in 

 opening up the immense pine forests of that part of Ontario. The 

 numerous lakes and rivers of the region were to be utilized in the 

 project. The work was carried on irregularly, abandoned and begun 

 again many times, and even today is far from completion. In the 

 meantime exploitation of the pineries outran the development of the 

 canal. The forests were cut clean and burned overmany times, so that 

 the canal itself was frequently damaged by the resulting floods. In 



