242 University of California Publications in Botuny [Vol. 8 



7. Monostroma orbiculatum Thur. 



Frond membranaceous, attached by fibrils, or later free ; soft and 

 flaccid, sub-orbicular or irregular in outline, often radially plicate, 

 with undulate margin, 30-40/a thick; cells angular, varying much in 

 size and arrangement, often irregularly elongate, closely set, but with 

 chromatophore not occupying the whole cell ; in cross section vertically 

 oval, 25-30ju. high. 



In brackish water attached to various objects in ditches of salt 

 marshes. Central California. 



Thuret, Note sur la Syn. Ulv., 1854, p. 388; Collins, Green Alg. 

 N. A., 1909, p. 212 ; Wittrock, Monostr., 1866, p. 39, pi. 2, f . 6. 



The present species resembles very closely the preceding and is, 

 in fact, to be distinguished from it chiefly by its greater thickness. It 

 may be a question as to whether it ought to be united with Monostroma 

 latissimum or not. So far as our experience goes, however, the M. 

 latissimwm plants are definitely not over 25ju, in thickness, and those 

 of M. orbiculatum seldom less than 35/i.. This seems to indicate suf- 

 ficient difference for keeping them distinct. 



8. Monostroma fuscum (Post, and Rupr.) Wittr. 



Frond membranaceous, at first tubular, soon splitting, dull green, 

 more or less lobed but not divided to the base ; membrane 20-35ju, 

 thick ; cells 4-6 angled, very closely set, in cross section quadrate, with 

 only slightly rounded corners, occupying nearly the entire thickness 

 of the frond. 



On stones in the middle littoral belt, and floating in salt marshes. 

 From Alaska to Puget Sound. 



Wittrock, Monostr., 1866, p. 53, pi. 4, f. 13; Collins, Green Alg. 

 N. A., 1909, p. 213; Saunders, Alg. Harriman Exp., 1901, p. 409; 

 Setchell and Gardner, Alg. N.W. Amer., 1903, p. 208. Ulva fusca 

 Post, and Rupr., Illust. Alg., 1840, p. 21. Ulv>a Lactuca var. rigida 

 Setchell and Gardner, Alg. N.W. Amer., 1903, p. 209 (in part). 



Monostroma fuscum var. splendens (Rupr.) Rosen v. 



Frond deep green, glossy, 50-55ju, thick, more deeply parted than 

 in the other forms ; cells similar to those of var. Blyttii or more 

 rounded. 



From Alaska to Vancouver Island. 



