1903.] The Cell Structure of the Cyanophycece. 403 



fibrils in the cytoplasm. But from a careful examination of the cells 

 of Phormidium retzii, in which the coloured granules are sometimes easily 

 seen, it appears to me that they are contained in the threads of the 

 cytoplasmic reticulum only, and that the definite arrangement in rows 

 is due to the uniform and regular distribution of the threads of the 

 reticulum between the central body and the cell wall. Nevertheless 

 the possibility of the existence of a filrillar structure in some forms is 

 not excluded, and I am not prepared to state definitely that it does 

 not occur. 



These coloured granules appear to contain both the colouring 

 matters which are known to occur in the Cyanophycese, chlorophyll and 

 anthocyan. Hegler considers them as special organs of the cell, and 

 suggests that they should be called Cyanoplasts, but it seems to me 

 that they may very well be compared to the " grana " which are 

 found in the chromatophores of such forms as Euglena, diatoms, &c.,* 

 the difference between them being that in the Cyanophycese the 

 " grana " are free in the cytoplasm, in other green plants they are con- 

 tained in specialised portions of it. This probably indicates that so 

 far as the colouring matter is concerned, we have in the Cyanophycese 

 not only a simpler, but also a more rudimentary type of structure 

 than in those forms with a specialised chromatophore or chlorophyll 

 grain. 



The Central Body. The central, colourless portion of the cell is 

 considered by many observers to represent the nucleus of the higher 

 plants, by others to be merely a colourless portion of the cytoplasm, or 

 a slightly differentiated portion of it. Whatever it may be it certainly 

 differs in appearance in the living state from the nucleus of the Algse 

 and higher plants, and, in fact, one of the arguments which might be 

 adduced against its nuclear nature is that in the fresh condition it 

 is so very easily seen, whilst the nuclei of some higher forms are 

 very difficult to make out in the living condition. The question of 

 the presence of a nucleus in the Cyanophycese is probably one of the 

 most controverted questions of recent years. So long ago as 1879 

 Schmitz announced the discovery, in the cell of a species of Gleocapsa, 

 of a homogeneous, deeply stainable, central mass, which he took to be 

 the nucleus. He came to the conclusion later, however, that this 

 could not be regarded as a true nucleus, but only as a chromatic 

 granule. Scottf and Zacharias,} working independently in 1887, came 

 to the conclusion that the central body represents the nucleus of the 

 higher plants. Zacharias was able to make out in some forms which 

 he examined a network-like structure, and demonstrated in it the 

 presence of nuclein, whilst Scott figured structures with a network and 



* See Arthur Meyer, ' Bot. Cent.,' 1882. 

 f ' Journ. Linn. Soc. Bot.,' 1887. 

 I ' Bot. Zeit.,' 1887. 



