84 University of California Publications in Botany [Vol. 6 



development and are as a rule blunt rather than acute, though more 

 or less abruptly tapering. The color varies from a delicate pink 

 through shades of red to a very dark red or reddish purple. The 

 diameter of the branches is nearly the same throughout and varies 

 from 2 mm. up to 12 mm. The branches are cylindrical in most 

 species and in some are constricted more or less regularly, giving a 

 moniliform appearance, while in certain species the branches are 

 evidently decidedly flattened or complanate. In many of the species 

 the branches are evidently or obscurely narrowed below, while in a 

 few the branches are conspicuously of the same diameter below as 

 above. The number of dichotomies varies in different species but less 

 so in individuals of the same species, and seems to be a diagnostic 

 character of value. 



At the tips of the branches are one, or usually two, circular, shallow 

 sunken areas which from growth proceeds by a multitude of filaments 

 exactly as in Galaxaura (Kny, 1872, p. 704; Oltmanns, 1904, p. 556). 

 but in one species of Scinaia the growing region seems convex (cf. 

 p. 102 of text). Below the tip is to be found an axile strand, stouter 

 or more slender according to the species and composed of few to many 

 coarser filaments longitudinally parallel or somewhat intertwined. 

 From these are given off slender, more or less horizontal filaments, 

 dichotomously branched and ending in the closely connecting cells of 

 the continuous cortex. Between the axile strand and the cortex is. 

 in the fresh condition, a sort of watery jelly filling the interior of the 

 branches. 



The structure of the cortex in Scinaia furcellata has been subject 

 to some discussion w^hich is outlined admirably by Bornet and Thuret 

 (1876, p. 19) and generally consists of one or more layers of colored 

 cells under an external compact layer of colorless cells. It is the 

 existence of this colorless epidermal layer that is said to distinguish 

 the genus Scinaia from Gloiopldoea J. Ag. 



The epidermal layer of colorless cells was not recognized by the 

 earlier algologists and there seems to be differences of opinion as to 

 its structure. Bornet and Thuret (1876, p. 20) describe the epidermal 

 layer as made up of colorless cells scattered between which are small 

 colored cells, but this structure is not shown in their figure {loc. cit., 

 pi. VI). Kuetzing, however, does show it (1866, pi. 68, h) in the way 

 it appears to the writer, and Crouan (1867, pi. H, f. 118, 6) also shows 

 the general appearance of colored and colorless cells in surface view. 

 The horizontal filaments from the axile strand end in corvmbs of .sliort 



