678 University of California PuMications in Botany \you 8 



This form has been collected but once. It grew in abundance on 

 a small rocky island in front of Sitka harbor and well up in the littoral 

 belt, exposed to the heavy action of the surf. The plants growing in 

 the most exposed places are quite arborescent in character, the alae 

 wearing away up to the last two or three segments, leaving the much 

 thickened midrib. In depressions and less exposed situations, the 

 alae are usually wider and remain longer on the fronds. The plants 

 in this group become exceedingly mucilaginous on being soaked out 

 after a thorough drying. 



3. Fucus edentatus De la Pyl. 



Fronds usually narrow, more or less flaccid, regularly dichotomous, 

 olive green to olive brown or yellowish, usually very black on drying ; 

 segments mostly decidedly linear, at times cuneate, midrib distinct, 

 percurrent, cryptostomata and caecostomata few or none, receptacles 

 mostly narrow, linear-lanceolate, acuminate, inflated or complanate. 



Growing in the middle and upper littoral belts. From Sitka, 

 Alaska, to Coos Bay, Oregon. 



De la Pylaie, Flor. Terre-Neuve, 1829, p. 84. 



Key to the Forms 



1. Midrib prominent, percurrent, segments reduced at each forking 



3. f. costatus (p. 680) 



1 . Midrib less prominent, segments not reduced at each forking 2 



2. Receptacles and segments widely divergent 2. f. divergens (p. 679) 



2. Receptacles and segments not widely divergent 3 



3. Fronds over 25 cm. high, receptacles often inflated 1. f. hesperius (p. 678j 



3. Fronds less than 25 cm. high, not inflated 4 



4. Fronds 9-15 cm. long, receptacles acute, 2-2.5 cm. long. 4. f. acutus (p. 680) 



4. Fronds 12-22 cm. long, receptacles subulate, 2.5-4.5 cm. long 



5. f. divaricatus (p. 681) 



1. Fucus edentatus f. hesperius Gardner 



Plate 103 



Fronds arborescent, 30-40 cm. high, narrow, coriaceous, dicho- 

 tomous, dark olive green, black on drying, stipe cylindrical; segments 

 strict, linear, 5-10 mm. wide, with truncate apices and well developed, 

 prominent, percurrent midribs, cryptostomata absent or extremely 

 rare ; receptacles mostly complanate, or in part much inflated, bi- tri- 

 furcate, linear, 3-4.5 cm. long, apices acute ; conceptacles numerous. 



