Vol. 2] Gardner. — Cytological Studies in Cyanophyceae. 261 



particularly during cell division, uniformly have a stronger avid- 

 ity for stain than other parts, and that these parts have a definite 

 procedure during every cell division. It has been found that 

 iron and phosphorus are constant constituents of the nucleus. 

 For the detection of these elements in the nucleus of the Cyano- 

 phyceae I have relied upon the careful investigation of Macal- 

 lum, who has demonstrated the presence of both masked iron and 

 organic phosphorus. These lines of evidences are corroborative. 

 The refractive body is not a homogeneous mass, but contains a 

 portion which has a strong affinity for " basic" stains, and con- 

 tains masked iron and organic phosphorus. This structure is 

 present as a constant organ in all living cells of the Cyanophy- 

 ceae, divides at each cell division, and, so far as can be judged 

 with, present knowledge at hand, it performs all the functions 

 of a cell-nucleus. In the mind of the writer this evidence seems 

 ample to warrant its being called a nucleus, and it will be treated 

 as such in the remainder of this account. 



The nucleus of the Cyanophyceae cell contains, in all of the 

 healthy vegetative cells of the forms studied, a ground mass, 

 granules, and chromatin. 



The ground mass of the nucleus has not been a subject of 

 special investigation in this study, and the writer is not prepared 

 to say much concerning the finer details of its structure and the 

 part it plays in the life phenomena of the cell, but from what has 

 been seen it seems to play no essential role in nuclear division ex- 

 cept to act as a matrix in which the other parts are at all times 

 embedded. 



The granules vary in size and number. There may be one or 

 more in each nucleus, according to the species and the conditions. 

 Of this more will be said under the head of granules. 



In any group of organisms in which there is a diversity of 

 morphological differences such as exist in the Cyanophyceae, one 

 would not expect to find the same nuclear differentiation through- 

 out the group. The variety of nuclear forms found in the groups 

 helps to confirm the universal belief in organic evolution, for 

 among the various members of the group we find instead of a 

 single pattern of nucleus a number of nuclear forms which may 

 merge into each other, but which indicate divergence from a com- 



