188 University of California Publications in Botany [^^"l. 8 



Hormisciu is closely related to both Chaetomorpha and Khizo- 

 cloniuni. From both of these it differs particularly in the pointed 

 posterior ends, or "tails," of the 4-ciliated macrozoospores. The 

 determination of this character is most satisfactorily made from living 

 specimens. It is possible, however, to be certain of it in dried speci- 

 mens of the mature fruiting stages if those are properly soaked out 

 and stained. In such specimens, it is often possible to ascertain the 

 shape of the zoospores with the conspicuous "tail" and in some cases 

 even to determine the number of cilia present if specimens have been 

 preserved in formalin solution. From Rhizoclonium, Hormiscia differs 

 in habit, in being attached at one end and erect, resembling Chaeto- 

 morpha in this respect. From Chaetomorpha, Hormiscia differs in 

 texture, being more flaccid or more lubricous. 



The species of Hormiscia resemble one another closely and are to 

 be separated by several minor characters. Those usually employed 

 are as follows: (1) chromatophores, (2) mode of attachment, (3) 

 diameters of the segments, and (4) shape and proportions of the seg- 

 ments. Besides there are some differences in height and texture to 

 be considered. 



The chromatophores of the species of Hormiscia are annular, 

 parietal, and single in the segment. They contain a larger or smaller 

 number of pyrenoids, more or less regularly placed. Some chromato- 

 phores seem practically imperforate, some are finely reticulate with 

 few or many small openings, while others are coarsely reticulate with 

 few or many large openings. Some species have thin, membranaceous 

 chromatophores, while others have thick, solid chromatophores. The 

 characters of the chromatophore also vary somewhat according to the 

 metabolic or reproductive condition of the segment. The study of 

 the chromatophore of specimens which have been dried presents cer- 

 tain difficulties, but usually they can be swollen up sufficiently and 

 stained (we use acid Fuchsin) to show their nature. Ordinarily it 

 is a fairly certain matter to determine whether a chromatophore is 

 coarsely reticulate or not. With the more finely perforate chromato- 

 phores, the difficulties are sometimes considerable. When dried speci- 

 mens are mounted fresh from the water before any collapse of the 

 protoplast has taken place, the chromatophore will swell out with 

 water and may plainly be seen. When segments in the filament 

 approach the reproductive condition, the chromatophore becomes less 

 and less perforate and also thicker, finally breaking up into areolae 

 (as seen from the surface) which precede the formation of either 



