1925] SetcheJI-Gardner: Melanophyceae 687 



5. Fucus evanescens f. robusms S. and G. 



Plate 107 



Fronds distinctly caulescent, 15-25 cm. high, much contorted, with 

 distinct stout stipe and holdfast, dichotomous, terminal portions 

 foliaceous, olive green to dark olive brown ; segments broadly cuneate, 

 terminal lobes rounded, 15-28 mm. wide, midrib distinct, slightly 

 reduced near the apices, alae membranaceous, cryptostomata sparse ; 

 receptacles broad, oblong, ovate or obcordate, very variable in size, 

 1.5-3.5 cm. long, complanate, or much inflated, not mucilaginous, with 

 distinct margin free from conceptacles w^hich are large and projecting. 



Growing on rocks in sheltered, shaded localities along extreme 

 high-tide limit. St. Paul Island, Alaska, to Friday Harbor, San Juan 

 Island, Washington. 



Setchell and Gardner, Alg. N.W. Amer., 1903, p. 283. Fucus 

 platycarpus? Setchell, Alg. Prib. IsL, 1899, p. 593; Gardner, Genus 

 Fucus, 1922, p. 47, pis. 49, 50. 



The type specimen was collected by Miss Ida M. Rogers, no. 5724 

 (Herb. Univ. Calif., no. 99133), at Sitka, Alaska. One of us (Gardner) 

 collected it at Sitka in June, 1910, when it was in full fruit, and at 

 Friday Harbor in July of the same year. The type and the two co-type 

 specimens have all of the receptacles complanate, and are apparently 

 immature, but in the other collections mentioned many of the recep- 

 tacles are much inflated. The species is one quite free from mucilage 

 as compared with other species of Fucus growing in the same localities 

 but much lower down in the littoral belt. It seems to have become 

 fixed as a form, and has the distinct habit, or character, of being able 

 to persist in the upper two feet of the littoral belt, in which habitat 

 it is necessarily uncovered the greater part of the twenty-four hours 

 each day. It inhabits rock ledges, either steep or sloping, yet it is 

 strictly confined to the upper, very narrow, belt. Its fronds are 

 lighter and somewhat more fibrous than those of any other form. 



6. Fucus evanescens f. stellatus Gardner 



Fronds decidedly flaccid, usually contorted, 25-35 cm. high, dicho- 

 tomous or subdichotomous, light brown below, yellowish above, dark 

 olive brown on drying, stipe and holdfast relatively small ; segments 

 relatively short, cuneate, wider toward the apices, 1.5-2.5 cm. wide, 

 midrib decidedly reduced above, cryptostomata few and inconspicuous ; 



