94 



MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



This is a very distinct species of Stigonema, with relatively 

 short, straight, and sparsely branched filaments containing a 

 single series of subspherical to much compressed cells, a thick 

 hyaline sheath, and consjjicuous, large heterocysts, a combina- 

 tion of characters most nearly approached by Stigonema elegans 

 and S. scytonem,atoides , both of this paper. 



Hapalosiphon tenuis sp. nov. 



Plate 23, figure 60 



Creeping filaments very profusely branched unilaterally, giv- 

 ing rise to numerous, erect filaments producing a compact stra- 

 tum ; erect filaments slightly tapering upwards, 175-225 \x long, 

 6-7.8 M diam. at the base, more or less branched near the base ; 

 trichomes 2.3-2.6 m diam. ; cells quadrate to 3.5 times as long as 

 the diameter, homogeneous, blue-green, cylindrical to somewhat 

 doliof orm ; sheath thin, firm, smooth, subgelatinous ; heterocysts 

 same shape and size as the cells, single or 2-3-seriate in the 

 creeping filaments or in the lower part of the erect filaments. 



Growing on serpentine rocks, forming a thin velvety stratum, 

 north of Sabana Grande, no. 943, type; on bark, Utuado, no. 

 1496. 



Hapalosiphon subgelatinosus sp. nov. 



Plate 23, figure 61 



Erect filaments numerous, sparsely branched, arising from a 

 more or less creeping filament, 10-14 |j diam., 200-250 p long, 

 nearly straight and parallel, in part attenuated, adhering to each 

 other somewhat by their subgelatinous sheaths into small fasci- 

 cles ; creeping filaments larger than the erect filaments ; cells 

 variable in shape and in size, cylindrical to dolioform, 5-10 \i 

 diam., the constrictions at the dissepiments extending to the 

 sheath, homogeneous, pale aeruginous ; sheath hyaline, thick, 

 homogeneous ; heterocysts conspicuous, slightly yellowish brown, 

 subspherical, mostly in the creeping filaments and in the lower 

 part of the erect filaments, 8-10 \\ diam. 



Growing on limestone between Arecibo and Utuado, no. 

 1476 f, type. 



