584 University of California Publications in Botany [Vol.8 



6. Coilodesma rigida S. and G. 



Plate 45, fig. 76, and plate 79Z> 



Fronds rigid, more or less coriaceous, complanate from the begin- 

 ning, and smooth, thickened along the margins, attenuated toward 

 the base into a thick, short stipe, broadened and rounded above, 5-10 

 cm. (up to 25 cm.) high, 1-2.5 cm. wide, 300-375/* thick, light brown 

 in color ; inner tissue composed of large, colorless, thick-walled cells 

 intermingled with numerous smaller filaments extending irregularly 

 in all directions, but toward the surface becoming smaller, perpendi- 

 cular to the surface and dividing di-trichotomously, terminating in 

 anticlinal rows of small, cortical cells ; zoosporangia irregular in form, 

 several times longer than broad. 



Epiphytic on Halidrys dioica Gardner in the upper sublittoral 

 belt. Redondo to San Diego, southern California. 



Setchell and Gardner, Phyc. Cont., VII, 1924, p. 9. 



Coilodesme rigida is one of the smaller species of the genus. It is 

 very firmly attached to the host by numerous deeply penetrating 

 rhizoidal filaments. It may readily be disting-uished by its rigid, 

 smooth, thick frond, usually thickest along the margin at maturity, 

 and by its complanate form from the beginning. It is of a decidedly 

 dark brown color, complanate from its early stages and, apparently, 

 confined to HaUdrys dioica as a host plant. The plant is smooth even 

 on the margins which, in the adult plant, are decidedly thickened, 



7. Coilodesme sitchensis S. and G. 



Fronds thin and flaccid, inflated, moderately undulate, 15-25 cm. 

 high, 3-6 cm. wide, cylindrical to slightly clavate, tapering abruptly 

 at the base into a slender short stipe ; color dark reddish brown, espe- 

 cially so on drying, internal tissue of 2 layers of large cells, cortex of 

 2-3 layers of smaller cells, radially elongated, both tissues bearing 

 chromatophores. 



Growing on CystophyUum geminatum (Ag.) J. Ag. Sitka, Alaska. 



Setchell and Gardner, Phyc. Cont., VII, 1924, p. 9. 



Cailodesme sitchensis occurs on the same host as C. linearis and 

 C. calif arnica. From the former it is to be distinguished by its broader 

 and more bullose habit and from both by its longer and more definite 

 stipe. It is also darker in color than C. calif ornica and rather more 

 bullose and undulated on the margins after collapsing. It may be 

 this species which was reported by Saunders on "CystophyUum 

 Lepidium" in localities north of the Puget Sound region. 



