BOOKS AND CURRENT LITERATURE 21 



question of the relative stimulating efficiency of light rays of different 

 wave length. The various observations on the effect of light upon 

 plants have been admirably summarized in tabular form by the author. 



The algae studied include various Euglena species, Phaciis triqueter, 

 Trachelomonas euchlora, Chlamydomonas globulosa, Gonium pedorale, 

 Pandorina niorum, Eudorina elegans and Spoiuhjlomorimi quaternarium. 

 In all of these forms certain spectral colors are much more effective 

 as stimulating agents than others. Thus for Pandorina morum (table 

 10, p. 509) the greatest response, calculated on the basis of equal energy, 

 is found in hght rays 524 /x^u long, the response diminishing rapidly 

 on either side of this point in the spectrum. This is correlated with 

 the luminous intensity, for if light on either side of the maximal point 

 in the spectrum is sufficiently intense it is more effective than the light 

 at the maximum. In any species the distribution of the response to 

 rays of different wave length is the same regardless of changes in phys- 

 iological condition, environment, or nature of response. The curious 

 point brought out by these investigations is, however, that the maxi- 

 mum is practically the same for certain species that are not closely 

 related {Euglena and Gonium) while closely related species {Gonium 

 and Pandorina) do not necessarily have the same maximum. 



The experiments were carried out in the Nela Research Laboratory 

 of the General Electric Company and the assistance which a purely 

 commercial company has given to a study of this type, which has no 

 apparent commercial value, is worthy of commendation by all scien- 

 tists. — Gilbert M. Smith. 



The Strawberry in North America.^ — Of particular interest to 

 horticulturists is the new work on the history, origin, botany, and 

 breeding of strawberries.^ There have been several attempts to trace 

 the origin of our cultivated strawberries of today. In his review of 

 the subject in 1896, L. H. Bailey remarked that ''Perhaps there is no 

 other plant which has more quickly obscured its own origin." The 

 author of the present work agrees with previous writers that three 

 species make up the possible foundation stock of our present varieties : 

 Fragariavirginiana, the common wild strawberry of Eastern North Amer- 

 ica; F. chiloensis, the Chilean berry native to the Pacific coast of both 

 North and South America, and F. ananassa the pineapple or pine straw- 

 berry which appeared rather mysteriously in Europe in the middle of 



' Fletcher, S. W. The strawberry in North America. Pp. xiv + 234, figs. 26. 

 The Macmillan Company; New York, 1917 ($1.50). 



