BOOKS AND CURRENT LITERATURE 125 



ration of the entire plant must be considered and not merely that of 

 the leaves; assimilation during winter is much more active than under 

 the same conditions in summer, as Miss Matthaei found also. By 

 using entire plants and outdoor air the author obtained assimilation 

 values that were much higher than those of Blackman, Matthaei or 

 Brown and Escombe, but which agree well with those of Thoday who 

 also used entire plants outdoors. The statement that the stomatal 

 opening changes in size when the wave length of the incident radiation 

 is changed throws doubt upon the results of previous investigations 

 dealing with the effectiveness of different portions of the spectrum in 

 photosynthesis. It may be mentioned that Ursprung 2 has recently 

 insisted that because of this stomatal behavior the question of the 

 photosynthetic effectiveness of radiation of different frequencies cannot 

 be settled by the use of plants possessing stomata. 



The weakest point in the work is, as the author recognizes, the 

 measurement of radiation. Although one of the most important con- 

 ditions of photosynthesis, radiation has never been measured in any 

 research on the subject in a way to yield real information. The author 

 used an Eder's photometer which is sensitive only in the blue-violet 

 region and guessed at the energy in the red portion. She recognizes 

 the inadequacy of the latter part of the procedure but does not appar- 

 ently realize that since the photometer had a curve of sensitiveness and 

 the light changed qualitatively, her results are not even of comparative 

 value in the region to which the photometer was sensitive. For this 

 reason simple photometers are worse than useless for measurements 

 of sunlight — the same reading at different times may not be due to 

 the same amount of energy. 



The research is a comparative one throughout, alpine and lowland 

 plants being investigated simultaneously, and from this standpoint the 

 work is excellent. The "theoretical" reasoning is, however, not very 

 convincing on the whole and shows how badly we need information on 

 the main features of photosynthesis. 



Perhaps one of the most important inferences to be drawn from the 

 paper is that, as has been found true in physical and physico-chemical 

 research, the organization of a system in which physical and chemical 

 events are expected to occur may be the condition deciding whether 

 and to what degree they can occur. The presence or absence of stomata, 



2 Ursprung, A., Ueber die Bedeutung der Wellenlange fur die Starkebildung. 

 Ber. d. b. Gesell. 36: 86-100. 1918. 



