466 University of (jalifovnia PubJicatioiis i)i Botanij [Vol. 6 



formation of gonidia is not unique in this species. It is similar to 

 that reported in this paper as taking place in Pleurocapsa entophy- 

 saloides, and in other undescribed species which I have observed. In 

 all of these species the contents of all of the cells of a colony seem to 

 divide simultaneously. Any and all of the vegetative cells may pro- 

 duce gonidia without change in size. This is true also of all species of 

 Dermocarpa, Gomphosphaeria, etc. The cell being small, the number 

 of gonidia from a cell is small, viz., 2-4, and it has not been deter- 

 mined positively whether the two divisions necessary to form four 

 gonidia take place successively or simultaneously. In most of the 

 species in other genera which I have studied, the divisions take place 

 successively, and this method may possibly be the one followed by all 

 species. Wille (1906, p. 21) has described and figured what appears 

 to be the same method of gonidial formation in the European Gloeo- 

 capsa crepidinum Thur., which he finds near the biological station at 

 Drontheim. He does not look upon this stage in the life-history as 

 being the gonidial stage comparable to that of the Chamaesiphonaceae, 

 but speaks of it as the ''ApAanocapsa-Stadium." He concludes that 

 these small cells float away, finally lodge in tide pools, and become 

 the so-called marine species of Aphanocapsa, e.g., A. marina Hansg. 

 The facts as we find them here seem hardly sufficient to warrant such 

 conclusions concerning our species. 



There are certain difficulties in the way of a satisfactory placing 

 of this form that have led to the disposition of it as a new species of 

 Pleurocapsa. Were it not for the presence of gonidia, it might be 

 placed fairly satisfactorily under Gloeocapsa crepidinuni Thuret. 

 The discovery of similar gonidia in what Wille refers to Gloeocapsa 

 crepidinum in Norway, strengthens this position. There are, however, 

 possibilities that Wille 's plant may not be the same as that of Thuret 

 and that ours may be different from both. Possibly all Gloeocapsa 

 species may be found ultimately to form gonidia, but it does not seem 

 very probable. In view of the various uncertainties, it seems best 

 for the present, at least, to describe the California plant as new and 

 to refer it to Pleurocapsa. 



Arthrospira breviarticulata Setchell et Gardner sp. nov. 

 Plate 39, fig. 18 and plate 41, fig. 26 



Trichomatibus in spiram plus minusve regularem laxissime con- 

 tortis, maxime et varie plus minusve dense implicatis, 14.5-16/x diam., 

 comparate brevibus, leviter, torulosis, non ad terminos attenuatis; 



