NEW MYXOPHYCEAE FROM PORTO RICO 



47 



does not branch. It seems best to place the specimen in the 

 genns Plectonema as a new species, awaiting more knowledge of 

 its life history. 



In company with this species is an nndescribed species of 

 Calothrix, and a very slender filamentous species of another 

 member of the Myxophyceae. The latter I forbear to j^lace. The 

 filaments are attached at one end and stand erect and parallel. 

 They are abont 1 n in diameter. Possibly they represent the 

 earlier stage of growth of Plectonema spirale. 



Plectonema murale sp. nov. 



Plate 9, figure 89 



Filaments much contorted and geniculate, 3.6-4 n diam., 

 branching sparse ; trichomes 1.5-1.8 jj diam., slightly constricted 

 at the cross-walls, not attenuated at the apices ; cells pale aerugi- 

 nous, quadrate to 2 times as long as the diameter; apical cell 

 blunt. 



Growing an the wall of a bridge, Juan Martin, Fajardo, no. 

 732 c, type. 



The material appears to have come nearly to the end of a 

 period of growth as the branching is decidedly sparse, and most 

 of the old connecting sheaths have disintegrated. The genicu- 

 late character of the filaments would indicate that branching was 

 abundant, and more or less perpendicular to the main axis. 



Plectonema flexuosum sp. nov. 



Pl^^TE 10, FIGURE 90 



Filaments not forming a stratum, more or less scattered 

 among other algae, 5.8-6.5 p diam. ; trichomes not constricted ; 

 apices not attenuated; cells quadrate to slightly longer than 

 broad, homogeneous, aeruginous ; cross-walls conspicuous ; api- 

 cal cells rounded to blunt-conical ; sheath very thin, white, 0.5- 

 0.8 M diam.; branching single, moderately abundant. 



Growing on soil in the woods, Coamo Springs, no. 272 h, type. 



Plectonema tenuissimum sp. nov. 



Plate 10, figure 91 



Filaments prostrate or scattered among other filamentous 

 algae, 1.4-1.6 (j diam.; trichomes slightly constricted at the dis- 



