Current Literature. 457 



scriptions of various photometers, notably those of Clements, 

 Wiesner and Zederbauer with some results of their use in America 

 and Europe. 



A plant physiologist might question the statement of the au- 

 thors that the measurement of the chemical light intensity by 

 photographic paper remains for the present the nearest approach 

 to the ideal in determining light values in a forest, for it is experi- 

 mentally known to him that the greatest activity in starch manu- 

 facture takes place under the influence of the r^ed rays whose in- 

 tensity, if measured at all, is measured but feebly by photographic 

 paper. And, moreover, according to investigations quoted in the 

 Bulletin, the rays of high refrangibility, whose intensity is meas- 

 ured by photographic paper, are absorbed by the superficial layers 

 of the leaf, but in the ordinary leaf most of the starch manufac- 

 ture takes place in the mesophyll which absorbs the rays of low 

 refrangibility screened out for it by the superficial tissue. Pho- 

 tometers, Ideally actinometers, may be nearest the ideal but they 

 have a long way to travel before they overtake it. 



American silviculturists and plant ecologists are greatly in- 

 debted to the authors for bringing together so much valuable data 

 concerning the fundamental but elusive problem of the light rela- 

 tions of trees. The Bulletin shows incidentally the position of 

 Americans as investigator's in the subject for it quotes two of 

 them and no less than twenty-five Europeans. 



C. D. H. 



This bulletin does not bring anything essentially new (except 

 record of a few measurements) and contains mainly what a good 

 course in biological dendrology or silvics should (yet perhaps 

 does not often) contain, but it is a very useful compilation of the 

 knowledge on a subject which is of great importance to the for- 

 ester. All the important data is assiduously brought together in 

 a clear and simple language and concisely and critically presented 

 on less than 60 pages. 



Half the space is occupied with an account of the attempts to 

 remove the determination of relative tolerance of species from 

 the realm of personal judgment or empirical methods to that of 

 actual measurements, physiological or physical. The authors 

 seem to be inclined to consider the photometric methods, such as 

 developed by Wiesner, Clements, Zederbauer and others, as most 



