476 BOTANICAL GAZETTE [june 



lence" or ability to fix nitrogen. The contradictory results of other investigations 

 are probably due to the use of different strains of organisms. The differences 

 between these strains are varietal or, possibly, even specific, for cultures from 

 various sources differ considerably in their nitrogen-fixing power. 



Beijerinck in his work on these organisms proposed a theory of symbiotic 

 activity between Azotobacter and other bacteria. Krzemieniewski concludes 

 that BeijErinck's results are to be explained not as due to the presence of the 

 second organism but to the addition of humus to culture solutions. 



These studies should serve to emphasize further the importance of soil humus 

 from the standpoint of agricultural practice. In addition to the solution of 

 certain puzzling questions, Krzemieniewski has opened several very promising 

 avenues for successful and profitable research in soil bacteriology.— Robert E. 



VHANW 



Mutability and variability. — Schouten 18 has an extensive account of two 

 years' Oenothera cultures. Seeds from DeVries, as well as commercial seeds 

 and "wild" seeds, and rosettes of various species were used. Several new mutants 

 appeared, and a number of interesting combination forms possessing the char- 

 acters of two types are recorded. The new mutants are O. blanda and O. cande- 



forms 



— - — / — — — • ' 



larcijolia nanella, O. rubrinervis brevistylis, O. rabrinervis lata, O. gigas nanella, 



and O. gigas lata (?). 



He makes the suggestion, which appears rather unlikely, that the nanella 

 or dwarf condition in 00. Lamarckiana, laevijolia, and gigas may be due to 

 bacterial action. O. Lamarckiana nanella is found to exist in two forms, differing 

 in their bud and flower characters. O. gigas is well known to show extremely 

 wide variability, particularly in leaf shape, and an attempt was made to segregate 

 several types, but without success, since the offspring from each showed nearly 



the whole range of variation. 



type 



gives a somewhat different appearance to the mutation phenomena in Oenothera. 

 Schouten concludes that mutants originate by two different methods: (i) When 

 both the gamete nuclei uniting in fertilization have the constitution of the same 

 mutant. (2) When the gamete nuclei are unlike. Of the latter he classifies two 



sorts 



other that of the mutant, (b) When both the gametes have a mutant constitution 



forms 



. > ""^ «*^«»«"6 «" tilt ^lllUiaauwn awxxx^. 



evidence is obtained from the fact that crossing increases the production ot 



mutants 



The third part of the contribution deals with statistical studies of variability 



Lamarckiana 



The parts 



measured include the length and breadth of certain stem leaves selected according 



A. — 1 /* * 1 1 « m 1 



petals 



18 Schouten, A. R., Mutabiliteit en variability, pp. 196. Groningen. 1908 



