1922] Setchell-Gardner : Phycological Contributions 385 



y. NEW SPECIES OF PYLAIELLA AND 

 STREBLONEMA 



Pylaiella tenella sp. nov. 

 Plate 42, figures 9-11 



Frondibus late diffiisis, simplicibus, 0.5-0.75 mm. altis, siiperne 

 longe-attenuatis, non piliferis, per filamenta curta, ramosa, contortaqne 

 affixis; eellulis 7-10/* diam., 1-2.5-plo. longioribiis quam latis; chro- 

 matophoris juvenis, singulis, intemipto-taeniatis, cellulam fere im- 

 plentibus, ultimo in frnstis distinctis separantibus ; zoosporangiis 

 longe-catenatis snbterminalibus. eellulis numerosis assimilatoribus in 

 seriebus per divisiones longitudinales zoosporangiis bina aut quaterna 

 f ormantibus ; gametangiis subterminalibus. 



Growing on Plcurophycus Gardneri Setchell and Saunders, the 

 plants forming minute tufts, which later become confluent. Neah Bay, 

 near Cape Flattery. AVashington. Type, Gardner, no. 3818 (Herb. 

 Univ. Calif., no. 207010), May. 



This species of Pylaiella is the most diminutive of all the known 

 species of the genus, rarely attaining the length of one millimeter, its 

 nearest rival, in this respect, being P. nana of Kjellman, from the 

 Norwegian Polar Sea. It differs from that species in size, being only 

 about one-half as large, in not being branched, in having subterminal 

 gametangia in a long series, instead of terminal branched ones as 

 described and figured by Kjellman for P. nana and in having double 

 and quadruple zoosporangia formed by longitudinal and cross divisions 

 of fructiferous cells. We have also observed this condition highly 

 developed in forms of P. littoralis. Double zoosporangia have been 

 observed by Borgesen (1920. p. 433) in P. fulvescens (Schousb.) 

 Bornet from the Danish West Indies. It evidently belongs to the 

 Panthocarpus group of the genus as established by Skottsberg (1915, 

 p. 158). The gametangia are formed by the transformation of vege- 

 tative cells, usually beginning relatively few cells back of the apices 

 of the filaments, a considerable number of cells transforming simul- 

 taneously. The transformation continues in both directions until one- 

 half to three-fourths of the filament is converted into gametangia. 

 They vary greatly in size, some producing as many as thirty-two loculi 

 from a single assimilating cell. They may be continuous or discon- 

 tinuous, certain assimilating cells in the series not being transformed. 

 The cell walls in the formation of loculi frequently are quite oblique. 



