458 University of California Publications in Botany [Vol. 8 



Myrionema corunnae Sauv. 



Fronds forming- small, circular cushions, 2-3 mm. diam., basal 

 disk monostromatic, not attached by rhizoids from below ; erect fila- 

 ments longest in the middle of the thallus, gradually reduced in length 

 toward the margin ; hairs scattered, relatively short, 4— S.S^u. diam. at 

 the base, cells 25-40/a long at the apex, meristem at the base but all 

 cells elongating at maturity ; all erect filaments fructiferous ; game- 

 tangia on 2-4-cened pedicels at the center of the frond, becoming 

 sessile toward the margin, mostly simple but not infrequently bearing 

 3-5 branches, 25-120/x, long, 4.5-7jii diam. ; zoosporangia unknown. 



Sauvageau, Sur quelq. Myrionem., 1897, p. 237 (repr. 1898, p. 77). 



The type material of the species was found growing in minute, 

 closely associated cushions on the outer ends of Laminaria pallida 

 at La Corogne (Spain), in November, 1895. We have not yet dis- 

 covered in our region any specimen which we can refer to typical 

 31. corunnae as described and figured by Sauvageau. The material 

 collected by one of us (Gardner) in December, 1909, growing on 

 Nereocystis Luetkeana (Mert.) P. and R., was identified by F. S. 

 Collins as belonging to that species and distributed in Phycotheca 

 Boreali-Americana (Exsicc.) as no 1738. Careful study of this 

 material reveals a mixture of several genera belonging to Myrione- 

 mataceae and Ectocarpaceae, none of which, so far as the specimens 

 in our copies go, is M. corunnae. Experience in collecting and 

 critical study of the numerous forms found, growing upon the above 

 mentioned host, have shown the necessity of exercising extreme care 

 in selecting pure or uniform material. The presence of branched 

 gametangia in typical M. corunnae, as diagnosed by Sauvageau, is a 

 character not found in any of our Pacific coast forms. 



The three following distinct forms have been segregated : 



3. Myrionema corunnae f. uni forme 



Fronds forming irregular cushions, 0.5-1.5 mm. diam. ; creeping 

 filaments forming a compact layer with peripheral growth ; hairs 

 absent; erect filaments unbranched, slightly attenuated at the apices, 

 80-100/x. (up to 120/a) high; cells of erect filaments 4.5-5. 5;li diam., 

 1-1.5 times a.s long; "ascocysts" sparse, clavate; gametangia forming 

 a solid, compact, palisade stratum of approximately the same height 



