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1923] Setchell-Gardner: Melcmophyceae 665
Key to the Forms
1. Caecostomata very numerous, 250-450 per square centimeter 2
1. Caecostomata less than 250 per square centimeter 4
2. Fronds cartilaginous, much crisped and twisted 5. f. contortus (p. 668)
2. Fronds tough, coriaceous, plane or nearly so 3
3. Fronds much branched, 10-18 mm. wide, 20-30 cm. high ...1. f. typicus (p. 665)
3. Fronds loose, 10-18 mm. wide, 30-50 cm. high 3. f. elongates (p. 667)
3 Fronds much branched, 15-30 mm. wide, up to 90 cm. high
2. f. luxurians (p. 666)
4. Receptacles cornute, wholly or in part 5
4. Receptacles not cornute 6
5. Segments linear, 5-6 mm. wide 10. f. cornutus (p. 671)
5. Segments cuneate, 18-24 mm. wide 9. f. nigricans (p. 671)
6. Young receptacles decidedly reflexed 7. f. reflexus (p. 669)
6. Young receptacles not reflexed «
7. Fronds 8-12 cm. high 11. f- abbreviates (p. 672)
7. Fronds over 12 cm. high 8
8. Fronds 4-12 mm. wide
8. Fronds over 12 mm. wide 10
9. Fronds 4-7 mm. wide, receptacles acute 13. f. angustes (p. 673)
9. Fronds 8-12 mm. wide, receptacles blunt 12. f. linearis (p. 672)
10. Segments increasing in width upward 8. f. latifrons (p. 670)
10. Segments diminishing in width upward H
11. Receptacles covering 3-4 terminal segments, linear 4. f. rigidus (p. 668)
11. Receptacles covering 1-2 terminal segments, very variable in shape
1. Fucus furcatus f. typicus Gardner
6. f. variabilis (p. 669)
Fronds somewhat caulescent, moderately cartilaginous, 20-30 cm.
high, regularly dichotomous, dark olive green, black on drying, seg-
ments plane, linear to cuneate, 10-18 mm. wide, midrib distinct, per-
current, caecostomata 250-300 per sq. cm., small, inconspicuous,
cryptostomata absent or very sparse; receptacles complanate, mostly
broadly linear, 4-6 cm. long, mostly bifid, apices acute ; conceptacles
very numerous and relatively small.
Growing on boulders and rock ledges in the middle of the littoral
belt. From the Strait of Juan de Fuca to central California.
Gardner, Genus Fucus, 1922, p. 16, pis. 2, 3. Fucus evanescens f.
typicus, Collins, Holden and Setchell, Phyc. Bor.-Amer. (Exsicc),
no. 1338. Fucus mflatus f. edentatus, Setchell and Gardner, Alg.
N.W. Amer., 1903, p. 280.
The Fucus furcatus of Tilden's American Algae, no. 234, as to
the specimen distributed in Professor Setchell's copy, is not typical of
this species as found on the California coast. The specimen is only a
small portion of a plant. It is mature, considerably worn and bat-
tered, and has comparatively few caecostomata. The distribution is