1917 Muenscherj Key to Phaeophyceae 271 



This plant can be distinguished from C. calif ornica because it grows 

 on rocks in the lower littoral zone and not on Cystophyllum as the former 

 species. Uncommon ; on Hankin Point, Shaw Island. 



18. COLPOMENIA Derbes & Solier 



1. CoLPOMENiA siNuosA (Rotli) Dcrb. & Sol. Mem. Phys. Alg. p. 11, pi. 

 22. Fig. 28 



Plant body a sessile, globose or oval thin sac, usually filled with water 

 when young; older plants forming hollow irregular masses two to ten 

 cm. across. Wall of the sac composed of two layers of tissue ; inner layer 

 consisting of a few large rounded colorless cells ; outer layer of small 

 quadrangular colored cells. 



Uncommon ; on rocks where they are exposed only at extreme low 

 tide, seldom on other algae. 



19. LEATHESIA Gray 



1. Leathesia difformis (L.) Aresch. Phyc. scand. p. 376. Fig. 29 



Plant body a sessile, globose or very irregular sac-like mass often 



more or less solid when young but becoming hollow with age. Central 



part of plant composed of repeatedly branched filaments which finally 



terminate in the outer layer of more or less cubical cells, paraphyses and 



sporangia. 



This plant is very often mistaken for Colpomenia but can usually 



be told from the latter by its thicker plant body and light brown color. 



However, a microscopic examination is often necessary to separate these 



two genera. 



Common on other algae especially Rhodomela LarLv and Fucus 



evanescent in the lower littoral zone. 



20. SCYTOSIPHON Agardh 



1. ScYTosiPHON LOMENTARius (Lyugbyc) J. Ag. Sp. 1: p. 126. Fig. 30 

 Plant body unbranched, tubular, one to eighteen dm. long, two to ten 



mm. thick; constrictions in tube regular and frequent or rarely almost 



entirely wanting; sporangia almost covering the entire surface of the 



tube. 



On rocks and stones in the lower littoral zone. 



21. MYELOPHYCUS Kjellman 



1. Myelophycus intestinalis Saund., Proc. Wash. Acad. Sci. 3: p. 420, 

 pi. 67. Fig. 31 



Plant cylindrical, hollow, more or less twisted, not constricted; one 



to three dm. long, narrowed into a solid stipe at the extreme basal end ; 



