igig] CURRENT LITERATURE 391 



One may doubt, however, whether the cuts protraying the features of Prince, 

 Rogers, and Munson flatter these leaders. As a whole, the book seems to do 

 well what it is intended to do. — Rodney H. True. 



NOTES FOR STUDENTS 



Cactaceae. — It is probable that no monograph of a family is based upon 

 more complete study than the monograph of Cactaceae by Britton and 

 RosE,^ the first volume of which has just appeared. The illustrations are very 

 numerous and admirable, and the colored plates are especially noteworthy. 

 The authors began the study in 1904, and since that time the field work 

 extended beyond North America, which was the original limit, so as to include 

 the arid regions of South America as well. Those who are acquainted with 

 the Cactaceae realize that not only are herbarium and field studies necessary, 

 but also greenhouse studies, to discover the different phases that may appear 

 during development. 



The present volume includes the tribe Pereskieae, with its single genus 

 Pereskia, represented by 19 species, 4 of which are new, and also the tribe 

 Opuntieae, in which 7 genera are recognized, one of which is new (Tacinga). 

 The large genus is Opuntia, with 264 species, grouped into 3 subgenera and 46 

 series, 32 of the species being new. New species are also described in Ptero- 

 cadus (3) and Nopalea (2). AU of the genera are illustrated, and of the 312 

 species 267 are represented by one or more illustrations. Of the 36 plates, 

 28 are in color. 



The investigation has been financed chiefly by the Carnegie Institution of 

 Washington, in cooperation with the New York Botanical Garden and the 

 United States National Museum, while the United States Department of Ag- 

 riculture has taken care of the living collections brought together in Wash- 

 ington. The completed monograph wiU consist of four volumes. — J. M. C. 



Zinc and growth of Aspergillus niger. — Steinberg^ finds that he gets 

 maximum growth in cultures of Aspergillus niger in flasks of Jena glass without 

 additions of zinc sulphate, while less than half maximum growth is given in 

 pyrex and Kavalier Bohemian glass flasks without zinc additions, and maximum 

 growth with such additions (10 mg. Zn/L). Steinberg thinks this is explained 

 by the fact that Jena glass contains considerable zinc, while the other glasses 

 do not. This accords with analysis of Jena and Kavalier Bohemian glass, 

 and with the experiments of other workers on the relation of zinc to the develop- 

 ment of this organism. He has also worked with 2 strains of A. niger, which 

 he terms W and Y, and finds that the former demands a higher concentration 



^ Britton, N. L., and Rose, J. N., The Cactaceae. Publ. Carnegie Inst. 

 Washington i: pp. 236. pis. 36. figs. 302. 1919. 



3 Steinberg, R. A., A study of some factors influencing the stimulative action 

 of zinc sulphate on the growth of Aspergillus niger. I. The effect of the presence of 

 zinc in the cultural flasks. Mem. Torr. Bot. Club 17:287-293. 1918. 



