12 Olive, Mitotic divisioii of tlie uuclei of the Cyaiiophyceae. 



of the conclusions liave already been given in Deceml)er in u 

 brief resume before tlie botanical section of the American 

 Association for the advancement of Science. 



I tako pleasui'e in acknowledgino- my great obligations to 

 the Carnegie Institution of "Washington for a grant, by means 

 of whicli I have been enabled to pursue these investigations in 

 the laboratory of Professor Strasburger. To Professor Stras- 

 burger particularly, for his many kindnesses and for his 

 unfailing interest and helpful advice; and to his assistant, 

 Dr. Max Koernike, and to others in the Botanical Institute of 

 the University of Bonn, I am also deeply indebted. 



Historical review. 



Among the thii'ty or more who have written on the cell 

 structure of these organisms, it is impossible to find any two 

 writers who agTce in all details. Indeed, in seeking to disentangle 

 the literature relating to this subject, one finds that several 

 authors even disagree witli their own earlier views. It is, 

 moreover, at times almost impossible to gain from the text an 

 author's exact meaning. For example, it is difficult in the 

 extreme to make certain, when Hieronymus used the expression 

 „the cyanophycin granulös represent the nucleus of higher plants", 

 whether lie really had in mind the cyanophycin granulös or the 

 slime globules, or „red granulös" of Bütschli. It is highly 

 probable, however, that he meant the latter. And it is, moreover, 

 not at all easy to follow understandingly Zukal's researches, 

 remarkable for their opacity, and interpret whether his many 

 nuclei in the cells of the Cyanophyceac were slime globules or 

 cyanophycin granulös; yet these two kinds of granulär inclusions 

 are readily distinguished from each other in their staining and 

 chemical reactions as well as in their location in the cell. 



In several of the more recent articles on this group, notably 

 in those of Fischer (97), Hegler (Ol), and Kohl (03), are 

 given excellent re views of the literature relating to the subject. 

 It has been thought better, therefore, for the purposes of brevity, 

 to present in tliis paper a table (pp. 2,3), Condensed mostly from 

 He gl er 's admirable review, showing very concisely the more im- 

 portant conclusions which have been reached with reference to 

 the principal topics concerning the cell, viz., the cyanophycin 

 granulös, the slime globules, the manner of distribution of blue 

 and green coloring matters, and lastly, the natm^e of that portion 

 with which the writer is in this paper more directly concemed, 

 the so-called „central body". In no other way, it seems to me, 

 can the astomiding confusion which prevails be so graphically 

 presented. Where great doubt exists as to the meaning of the 

 author, I have foUowed my Interpretation with a question (?). 

 Later, the views of several writers will be more fully discussed. 



Material and methods. 



The material for the present research was coUected for the 

 most part in green houses, the large OsciUatoria princeps from 



