and Laboratory Methods. 2701 



single nucleus. Each of the four cells of the promycelium produces a uni- 

 nucleated sporidium. The first division of the nucleus of the sporidium is not 

 followed by cell division, but starting with the sporidium there is developed a 

 mycelium of binucleated cells. In short, from teleutospore to sporidium the 

 cells are uninucleated, and from sporidium to teleutospore, binucleated. 



The two nuclei which fuse in the teleutospore maintain a separate existence 

 throughout almost the entire life cycle of the rust, and there is some evidence 

 that the chromosomes in the division of the fusion nucleus are collected into two 

 groups, representing, possibly, the chromosomes of male and female nuclei. 

 While there is no proper cell fusion, the union of nuclei more or less separated 

 in origin is not out of harmony with our conceptions of sexual reproduction in 

 other groups of plants. c. j. c. 



Kohl, Dr. F. G. Ueber die Organization und The structure of the Cyanophyceae and 



Physiologic der Cyanophyceenzelle und die n ^ • i ^ i_ i_ • ^ r 



mitotische Teiluni ihres Kernes. 8vo. pp. Bacteria has long been a subject of 



240, 10 pis. Gustav Fischer, Jena, Gar- dispute, and the observations, interpre- 



many, iqo^. Price, 20 marks. ^ ^. , . , . , , n- . 



■^ ^ -^ tations, and theories have been conflict- 



ing and contradictory. Some writers have described nuclei and chromatophores 

 while others have denied the existence of such organs, and in regard to other 

 structures only less difference of opinion has prevailed. 



Dr. Kohl gives a critical review of the work of previous investigators and 

 presents the results of his own extensive investigations, which deal chiefly with 

 Tolypothrix, Nostoc and Anahaena. Without attempting to separate original views 

 from confirmations and contradictions, the author's conclusions, as found in his 

 summary and in the body of the work, are about as follows : The protoplast of 

 the Cyanophyceae does not differ essentially from that of other plant cells. It 

 has a nucleus and peripheral cytoplasm containing chromatophores. There is 

 always a single nucleus in a cell, and it is an independent organ of the proto- 

 plast. The nucleus consists of a relatively faintly staining ground mass in which 

 the chromatin is embedded ; the nucleus also contains a larger or smaller 

 number of "central granules " which are never found outside the nucleus. The 

 nucleus differs from that of higher plants in having no nuclear membrane or 

 nucleolus and in its form. The cytoplasm contains numerous chromatophores, 

 cyanophyceae granules (Cyanophycinkorner), glycogen and vacuoles. The 

 chromatophores contain chlorophyll, carotin and phycocyan. The product of 

 assimilation is glycogen ; starch is not demonstrable. The membranes of the 

 vegetative cells consist principally of chitin, and those of the heterocysts con- 

 sist largely of cellulose. The oft discussed central body is a genuine nucleus. 

 During mitosis a spirem is formed which breaks up into a somewhat definite 

 number of chromosomes. The phases resemble those of the higher plants, and 

 the author refers to them as the spirem, equatorial plate dyaster and dispirem. 

 Threads resembling a spindle are described and figured. 



The writer believes that chromatin is a constant constituent of the cells of 

 the Bacteria as well as of those of the Cyanophyceae, and believes that the 

 CyanophycCcC and Bacteria are very intimately related. 



The methods are described in full, but are too technical to be condensed 



