



1920] 



CURRENT LITERATURE 











323 



Chemical stimulation. — Steinberg I2 has reported on further studies on 

 the chemical stimulation of growth in Aspergillus niger, especially as brought 

 about by Zn and Fe salts. Pfeffer's nutrient solution was used as the basis of 

 all cultures. Commercial reagents, without further purification, were used 

 in making solutions. It was found that o . 1 to 1 . o mg. Zn per liter was 

 sufficient to furnish maximum stimulation, the growth thus stimulated avera- 

 ging about four times that of the check. Successively lessening the amounts of 

 each of the inorganic constituents of the solution resulted in all cases in de- 

 creased yield, showing none of them present in toxic or super-optimum con- 

 centration. Increasing the concentration of the various salts stimulated 

 growth, although to a much less extent than that caused by Zn. Decreasing 

 the acidity by adding alkalis decreased growth and gave strong spore forma- 

 tion. Increasing the H ion concentration by adding various acids stimulated 

 vegetative growth and decreased spore formation. The type of growth 

 resulting from increasing H ion concentration was very similar to that follow- 

 ing Zn stimulation, but was always less in amount. Steinberg believes the 

 H ion concentration of Pfeffer's solution to be sub-optimum for A . niger, and 

 suggests that the increased acidity of the solution with the addition of salts 

 of the heavy metals with strong acids may be a very important factor in the 

 stimulation to greater growth. 



The Pfeffer solution was purified by autoclaving with CaC0 3 to precipitate 

 Zn and other bivalent metals. Growth in such solutions was much less than 

 in those not purified. Either Zn or Fe added alone stimulated growth some- 

 what, but not nearly so much as when both were added. Growth in the latter 

 case was equal to that in any of the non-purified Zn stimulated cultures. 

 Steinberg believes previously secured stimulation from Zn alone to have 

 been in the presence of Fe impurities. 



No analyses were made to determine the chemical changes associated 

 with the marked variation in growth rate and form brought about by the 

 variation in the nutrient solution. Such data would be most interesting. 

 It is unfortunate that reagents were not sufficiently repurified to eliminate 

 entirely the possibility of Zn, Fe, Ni, and other such metals in the basic 

 nutrient solution. — J. R. Magness. 



Mangroves. — Among the interesting features of a study of the red man- 



grove, Rhizophora Ma 



the historical 



development of our knowledge of the tree. The literature dates from 325 

 B.C. to the present, and includes references by Theophrastus, Plin^ 

 Plutarch, Bauhin, Ray, LINNAEUS, and Lamarck, as well as more recent 

 writers. 



Steinberg, R. A., A study of some factors in the chemical stimulation of the 

 growth of Aspergillus niger. Amer. Jour, Bot. 6:330-372. 1919. 



13 Bowman, H. H. M., Ecology and physiology of the red mangrove. Proc. 

 Amer. Phil. Soc <6:;8o-672. Us. 0. ioi7. 



