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(J!)() University of California Publications in Botany [Vol.8
Setchell and Lawson, no. 5151 (Herb. Univ. Calif., no. 99110),
Orca, Alaska. Collins, Holden and Setchell, Phyc. Bor.-Amer.
(Exsicc.), no. 928; Setchell and Lawson, no. 5186 (Herb. Univ. Calif.,
no. 99109), Juneau, Alaska.
This form is unlike all other forms in the extremely long, linear-
lanceolate, regular, complanate receptacles, frequently spreading or
recurved at the apices. In external appearance it approaches jP.
furcatus f. rigid/its, but that form has an abundance of caecostomata,
the receptacles more decompositely furcate, and it is more cartilaginous.
10. Fucus evanescens f. marginatum Gardner
Fronds distinctly caulescent, 20-50 cm. high, regularly and
repeatedly dichotomous, decidedly rigid and coriaceous, much con-
torted, yellowish brown, very dark olive brown on drying, stipe terete,
tapering upwards among the branches; segments 9-15 cm. wide, strict,
not narrowing above forking, truncate, mostly long, linear, midrib
moderately prominent, slightly evanescent, alae wearing away un-
evenly, cryptostomata almost absent ; receptacles 1.5-3 cm. long,
definitely delimited, single or deeply bifurcate, narrowly ellipsoidal,
marginate ; conceptacles very prominent.
Growing on rocks in the middle littoral belt. Sitka, Alaska.
Gardner, Genus Fucus, 1922, p. 42, pi. 42.
The distinguishing characters of this form are absence of con-
ceptacles from a complete margin of the receptacle, particularly of
the rounded terminal portion, coupled with extreme sparsity of both
cryptostomata and caecostomata.
It is difficult to decide to which species this form is most closely
related. It has evident affinities with Fucus evanescens Ag. and with
F. spiralis L. Its color and consistency, coupled with the slightly
vanishing midrib in the terminal segments, seem to ally it with F.
evanescens, but, if allied with this species, it would be through f.
dendroides of Stroemfelt as its nearest relative. We have not seen
the type nor any authentic specimens of f. dendroides, but since no
one has questioned the validity of the form as belonging to F.
evanescens, we are retaining it as such and grouping certain Alaska
specimens with it. The narrow, rather long, considerably contorted
and profusely branched fronds, the blunt and somewhat fusiform
receptacles, and the dendroid habit certainly suggest its close simi-
larity with f. dendroides. However, we are inclined to keep it distinct