jtineis, I9I5 Azotohacter Chroococcum 227 



environmental conditions. With the object in mind of clearing up this 

 point, a brief review of the literature on the cytology of A. chroococcum 

 is submitted. 



HISTORICAL REVIEW 



Beijerinck (2) early described Azotohacter chroococcum with regard to 

 its morphology. With the aid of Prof. Zetnow, he determined that the 

 organism was capable of movement by means of a polar cilium. This 

 author describes sarcina-like packets in cultures of A. chroococcum and 

 also points to the supposition that these might be resistant forms to 

 replace the spore stadium, which is not present in this organism. These 

 same packets were observed by Krzemieniewski (10, p. 932-941), who 

 found, furthermore, that the cells escaped later from their envelope, 

 leaving it like an empty sheath. Their resistant nature was to some 

 extent doubtful. 



A very interesting contribution to the cytology of A . chroococcum was 

 made by Prazmowsky (15), who used nearly exclusively vital staining 

 with methylene blue to determine the structure of this organism. He 

 observed the division of what he called "nuclei" (which, according to 

 the description, are Heinze's (8, p. 57) glycogen granules, Ashby's (i) 

 glycogen granules, H. Fischer's (5) volutin granules, and Mend's (11) 

 nuclei) in the cells of this Azotobacter and stated that the division of 

 this nucleus was followed by the division of the entire cell. By this 

 means were formed chains of elements, which later separated in single 

 individual cells. Prazmowsky denies completely the presence of glycogen 

 in vegetative cells of A . chroococcum, but admits its presence in the cells 

 representing the resting stage of the organism — the so-called arthro- 

 spores. He holds to the presence in nature of three types of cells of A . 

 chroococcum: (i) Nuclear cells {Kernzellen) , (2) alveolar cells {alveolar e 

 Kernzellen), and (3) cells with a diffused nucleus (diffuse Kernzellen). 

 Some drawings presented by Prazmowsky (15) resemble the sarcina-like 

 packets described by Beijerinck (2) and pictured by Krzemieniewski (10). 



Jones (9) holds views completely different from those of all the preced- 

 ing authors. He considers the granules within the cells of A . chroococcum 

 to be of two kinds, one kind, more often found, consisting of glycogen, 

 and the other of a substance that makes up the body of what the author 

 calls "gonidia," which are capable of flowing from the mother cell and 

 are provided with very long delicate cilia. 



Mencl, in his work already mentioned (11), used the same staining 

 methods as Prazmowsky (15), and came to the same conclusions as that 

 author. 



From this very brief summary of the literature on the subject it is evi- 

 dent that opinions as to the constitution of the cellular make-up of A. 

 chroococcum differ widely. 



