346 University of California Publications in Botany [You i 



Growing on the outer ends of the leaves of eel-grass, in company 

 witli other small algae, in the lower littoral belt. Sitka, Alaska. Type, 

 Gardner, no. 89G8c (Herb. Univ. Calif., no. 207016), July. 



M\irwncm,a sctiferum is undoubtedly very closely related to M. 

 phyllophihun on the one hand, and to M. foecundum f. californicum 

 on the other. From the former, it differs in having longer and nar- 

 rower erect filaments with longer cells and in having much longer and 

 narrower gametangia which are more frequently borne laterally on the 

 erect filaments, and often fasciculately branched from a short pedicel. 

 From the latter, it differs in having functional zoosporangia, one of 

 the few instances in which we have actually seen the undoubted 

 zoospores, in having longer and setiferous erect filaments, and longer 

 and slightly narrower gametangia. 



Myrionema obscurum sp. no v. 



Plate 32, figure 6 



Frondibus microscopicis, supra superfieiem hospitis irregulariter 

 dispersis; filamentis repentibus multo ramosis, maxime compaetis et 

 contortis, stratum pseudo-parenchyinaticum formantibus ; filamentis 

 erectis sparsis, simplicibus, 40-70/x altis; pilis veris ignotis; eellulis 

 filamentorum repentium forma magnitudineque maxime irregularibus, 

 4.5-10/A diam., eellulis filamentorum erectorum cylindricis, 6.5-7.5/x 

 diam., exacte aut fere quadratis; zoosporangiis numerisissimis. in 

 filamentis repentibus, sessilibus, ovoideis usque ad late clavatis, 45-65/* 

 longis, 18-30/i, latis; gametangiis ignotis. 



Growing on the blade of Costaria costata. Moss Beach, San ^Mateo 

 County, California. Type, Gardner, no. 4315 (Herb. Univ. Calif., 

 no. 207021), July. 



Myrionema obscurum seems decidedly distinct from all other species 

 of the genus. It seems to be a near relative of M. strangulans Grev. 

 The basal layer is very compact, and adheres very firmly to the host, 

 following closely the irregularities on its surface. We are unable to 

 make out whether or not the epiphyte causes the death of tlie cells of 

 tlic liost, which seems to be quite frequent in all of the plants we have 

 observed. Tlie creeping filaments push among the dead cells of the 

 host at times. The zoosporangia are numerous and all sessile. 



