NEW MYXOPHYCEAE FROM PORTO RICO 



93 



Stigonema tuberculatum sp. nov. 



Plate 21, figure 55 



Filaments 200-300 m long, 14-18 [x diam. in oldest parts, 

 crooked, irregular, and tiiberculate ; cells spherical, 1-4-seriate, 

 olive-green, 5-7 m diam. ; sheath thin, close-fitting, hyaline. 



Growing on rocks near Maricao, no. 1030, type. 



The plants of this species have the peculiar habit of not read- 

 ily wetting or absorbing water; seemingly waxy. 



Stigonema opalescens sp. nov. 



Plate 22, figure 58 



Filaments moderately crooked, long-arcuate, smooth, 450- 

 650 n long, about 25 \x diam. ; cells subspherical, mostly 4-seriate, 

 7-8.5 (J diam., bluish-green, homogeneous, protoplasmic connec- 

 tions distinct; sheath uniformly opalescent, even and smooth 

 along the surface, ample; heterocysts very sparse; branching 

 very sparse. 



Growing on rocks near Maricao, no. 1033, type. 



The long, arcuate, smooth filaments with few branches and 

 the opalescent sheath are sufficient to distinguish this species 

 of Stigonema. The division of cells is somewhat spasmodic, not 

 uniform throughout the filament. It is a common occurrence 

 that one, two, three, or four cells in a node in the body of the 

 filament may be present. 



Stigonema parciramosum sp. nov. 



Plate 23, figure 59 



Filaments 300-450 n long, 23-27 \.\ diam., not tapering, 

 branches very sparse, similar to the main filaments, not con- 

 stricted at the base ; cells compressed-spherical, 17-19 m diam., 

 one-half to two-thirds as long as the diameter, pale aeruginous, 

 homogeneous, strictly uniseriate in the filament except where 

 branches arise, contiguous or slightly separated when old ; het- 

 erocysts fairly numerous, of the same shape and size as the cells ; 

 sheath thick, hyaline, homogeneous, subgelatinous. 



Growing among other sjiecies of Myxophyceae, e.g., 8cy- 

 tonema javanicum, on lava north of Sabana Grande, no. 921 a, 

 type. 



