404 University of California Publications in Botany [Vol.8 



use the binomial itself and we follow custom in citing as authority the 

 first writer known to us to do so. . 



Pylaiella littoralis, as usually recognized, is a very variable and 

 widespread species. In height, it varies from a few centimeters up to 

 six decimeters or more ; in color, from light yellowish brown to very 

 dark brown; in habit from a feathery frond of loosely entangled fila- 

 ments, through tufted masses to rope-like aggregations; in branching 

 from very abundant, opposite or alternate, to comparatively scanty 

 and chiefly alternate ; and in angle of branching, from narrowly acute 

 to broadly obtuse, erect, ascending or even recurved. There is con- 

 siderable variation in the diameters of the primary filaments and in 

 the dimensions and position of the zoosporangia and gametangia. It 

 is difficult, or even impossible at present, to determine how much of 

 this variation is due to age and environment and how much may be 

 of genetic significance. There are several varieties described with 

 more or less definiteness, and few to several forms under each. Earlier 

 (1903), we attempted to refer as many of the plants of the north- 

 western coast as possible to their proper forms. At present, it seems 

 to us undesirable, as well as very unsatisfactory, to attempt this. The 

 var. opposita Kjellm., loose in habit and with abundant, chiefly 

 opposite, branching, may be taken as including the normal, or also 

 even the taxonomic, type. The var. firma (Ag.) Kjellm. is also lax 

 in habit but with less abundant and more scattered branching. Var. 

 divaricata Kjellm. is more commonly funiculose or ropy and with the 

 branches irregularly placed, often incurved and geniculate. The 

 forms of var. varia (Kjellm.) Kuck. seem the most distinct in their 

 peculiarly aggregated gametangia and contorted funiculose habit. 

 Forms of all four, and perhaps even of other varieties, occur on our 

 coast and a study of the same plants over a series of weeks or months, 

 or in cultures, would undoubtedly assist much in elucidating the 

 significance of the great variation credited to this species. 



2. Pylaiella unilateralis S. and G. 



Erect filaments attached by creeping, irregular, more or less 

 branched filaments, tufted, slightly clavate, 4-7 mm. high, 19-22^ 

 diam, at the bases, 28-32^ diam. at the apices; branching mostly 

 alternate and sparse below, secund above, and arising from cells 

 divided longitudinally 1-2 times; cells 2-2.5 times as long as the 

 diameter and cylindrical at the base, more or less quadrate and doli- 

 iform above; ehromatophores thin, irregular plates more or less con- 



