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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 I ill oral is, 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 garnet angia. 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/x 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 ; chromatophores thin, irregular plates more or less con-