1925] Setchell-Gardner : McJunophyceae 675 



2. Fucus membranaceus f . latissimus Gardner 



Plate 105 



Fronds foliaceous, membranaceous, crisped, dichotomous, 22-25 

 cm. high, dark olive green below, changing to yellowish brown above, 

 holdfast comparatively small, stipe flattened; segments slightly ovate 

 above, narrower and cuneate below, subterminal 4—6 cm. wide, midrib 

 relatively narrow, percurrent, alae thin, membranaceous, frequently 

 inflated with gas, margins undulate, apices round and smooth, grow- 

 ing point inconspicuous, cryptostomata 15-20 per sq. cm., producing 

 abundant protruding paraphyses, prominent on drying; receptacles 

 sparse, complanate, not definitely delimited, widest at the base, bi- 

 tri-furcate. 



Growing on boulders in the extreme lower littoral belt. Kadiak 

 Island and Sitka, Alaska. 



Gardner, Genus Fucus, 1922, p. 35, pis. 33, 34. 



In June, 1910, Gardner first observed this form growing in the 

 harbor at Sitka, but at that time was unable to obtain good fruiting 

 specimens. On his second visit to the same place in July, 1917, he 

 located a large bed containing thousands of plants growing along the 

 extreme low-tide level, and was able to procure a number of good 

 fruiting specimens, although the summer season does not seem to be its 

 best fruiting season. This form may be readily distinguished from all 

 others by its width, being the widest of all forms, its membranaceous 

 alae, its very dark lower portion, and usually yellowish upper portion, 

 and by its much crisped habit of growth. Some of the plants of this 

 species collected by G. B. Rigg at Kadiak Island are the widest speci- 

 mens of Fucus that have been reported, some of the fronds measuring 

 over seven centimeters in width. 



3. Fucus membranaceus f . limitatus Gardner 



Fronds distinctly membranaceous, 22-32 cm. high, dichotomous, 

 light yellowish brown, dark brown on drying, stipe and holdfast 

 fragile ; segments strict, mostly cuneate, usually wider at each suc- 

 cessive forking, 12-20 mm wide, terminal lobes rounded, growing 

 point slightly depressed, midrib not prominent, alae thin, crypto- 

 stomata very sparse and inconspicuous; receptacles mostly inflated, 

 bifid, apices acuminate, usually divergent, very variable in size, up to 

 5 cm. long and 2 cm. wide ; conceptacles scattered and not prominent. 



