1925] Setchell-Gardner: Melanophyceae 677 



F. evanescens f. bursigcra, also collected at Spitsbergen. The plants 

 of Agardh and of Kjellman are undoubtedly of the same lineage, and 

 they are probably allied more closely to the evanescens lineage than 

 to any other. The Sitka plants under consideration, on the whole, and 

 particularly on account of size and consistency, seem closer to the 

 membranaceus group than to the evanescens group. The two groups 

 certainly overlap through these two forms. 



5. Fucus membranaceus f. obtusus Gardner 



Fronds slender, more or less caulescent, membranaceous, 30-40 cm. 

 high, dichotomous, olive green to dark brown, very dark on drying; 

 segments strict, linear to slightly cuneate, relatively long, 10-16 mm. 

 wide, midrib percurrent, alae thin, cryptostomata and caecostomata 

 nearly equal in number, 30-40 per sq. cm., small, papillate on drying ; 

 receptacles definitely delimited, much inflated, mostly single, in part 

 bifid, 2.5-4 cm. long, 1-1.5 cm. wide, blunt, yellowish brown; con- 

 ceptacles not numerous, comparatively small, not protruding. 



Growing on rocks in the middle and lower littoral belts. Sitka, 

 Alaska. 



Gardner, Genus Fucus, 1922, p. 34, pi. 29. 



This form has characters linking together forma aeuminatus and 

 forma typicus of this species. It has the arborescent habit common to 

 both forms, the width of the fronds is intermediate, and the receptacles 

 are mostly simple and blunt, unlike either form. 



6. Fucus membranaceus f. acuminatus Gardner 



Fronds caulescent, 12-20 cm. high, profusely branched, dicho- 

 tomous to subsecund, dark brown to yellowish brown; segments very 

 slightly cuneate to linear, 4-9 mm. wide, truncate, midrib well 

 developed below, somewhat reduced just below the receptacles, alae 

 thin and membranaceous, cryptostomata varying from few to 50-60 

 per sq. cm., mostly on the segments just below the receptacles, absent 

 in the older parts, very small but conspicuous on drying ; receptacles 

 numerous, regularly and deeply furcate, or, rarely, single, mostly 

 complanate, narrow, acute, 2-3 cm. long; conceptacles relatively 

 numerous. 



Growing on rock ledges exposed to heavy surf, in the upper 

 littoral belt. Sitka, Alaska. 



Gardner, Genus Fucus, 1922, p. 33, pi. 28. 



