NEW MYXOPHYCEAE FROM PORTO RICO 



87 



Tolypothrix robusta sp. nov. 



Plate 20, figure 49 



Filaments more or less matted together, forming a pannose 

 stratum, 1-2 mm. long, 22-30 [i cliam., straight or arcuate, fairly 

 rigid ; trichomes 12-18 p diam., the smaller diameter in the older 

 parts of the filament, the larger at the apex, constricted more or 

 less at the dissepiments; cells very short, 2-4 m long in the meris- 

 tematic region, quadrate in the older parts, bright aeruginous, 

 densely and finely granular; heterocysts of the same size and 

 shape as the cells; sheath hyaline, homogeneous, and subgelati- 

 nous when young, changing to lamellose and becoming succes- 

 sively colored brown from the trieliome outward. 



Growing in association with other algae in Laguna Tortu- 

 guero, no. 827, type, and no. 820. 



Tolypothrix Willei sp. nov. 



Plate 20, figure 50 



Filaments growing in microscopic tufts among other algae, 

 up to 1 mm. long, 7-8.5 m diam., sparsely branched ; trichomes 

 2.4-2.6 |j diam. in the older parts, 4.2-4.6 m diam. at the apices; 

 cells quadrate to 3.5 times (up to 6 times) as long as the diam- 

 eter, cylindrical when mature, slightly dolioform in the meris- 

 tematic region at the apex of the trichome, mostly homogeneous ; 

 apical cell frequently subspherieal ; heterocysts sparse, of the 

 same shape and size as the cells ; sheath relatively thick, hyaline, 

 homogeneous. 



Growing in a reservoir west of the Experiment Station, Eio 

 Piedras, no. 209 a, type; in a pool in Jayuya, no. 1649 a. 



Tolypothrix Willei apparently is a close relative of T. fasci- 

 culata Gomont. It does not form the fascicles characteristic of 

 that species, is shorter and narrower, and has much longer cells 

 in the older parts of the trichomes. 



Stigonema hormoides constrictum var. nov. 



Filaments short, crooked, slightly branched, 11-13 m diam., 

 constricted at the dissepiments ; cells quadrate to one-half as 

 long as the diameter, slightly constricted when young, becoming 

 much more so with age, pale grayish green; hormogoniferous 

 branches very short ; sheath very thin, hyaline or slightly colored 

 when old. 



