1922] Gardner: The Genus Fucus on the Pacific Coast '6'i 



principally in having shorter fronds, relatively much broader and 

 shorter receptacles, fewer cryptostomata, and it is less mucilaginous. 

 It seems closely akin to J. Agardh 's Fucus bursigerus from Spitz- 

 bergen, but it is more robust, and much more profusely branched than 

 his description and figure call for (cf. J. Agardh, Spets. Alg. Till., 

 1S6S, pp. 41, 42, pi. 3). I have seen the specimen of Kjellman's F. 

 evanescens f. bursigera, also collected at Spitzbergen. 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 

 mcmbranaceus group than to the evanescens group. The two groups 

 certainly overlap through these two forms. 



Fucus membranaceus f. acuminatus f. nov. 



Plate 28 



Frons caulescens, 12-20 cm. alta, decomposite dichotorna, ramos- 

 sima, brunnea aut fulva ; segmentis paullo cuneatis interdum linearibus, 

 4—9 mm. latis, truncatis, costa in partem inferiorem clistincta, infra 

 receptaculis diminuatis, alis tenuibus membranaceis, cryptostomatibus 

 paucis vel 50—60 in quoquo cm. quadrato, saepissime infra receptaculis 

 ad segmenta, ad partes vetustas deficientibus, minimis, siccatis eviden- 

 tioribus; receptaculis numerosis, regulariter et profunde furcatis vel 

 interdum unicis, saepissime complanatis, angustis, acutis, 2-3 cm. 

 longis; conceptaculis numerosis. 



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

 belt. Sitka, Alaska. 



Type, Gardner, no. 3995 (Herb. Univ. Calif., no. 201177), July, 

 1917. 



This form was encountered but once. It was growing in abundance 

 on a small rocky island in front of the Sitka harbor. It grew 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 were usually wider and remained on the fronds 

 longer. The plants in this group become exceedingly mucilaginous on 

 being soaked out after a thorough drying. 



