80 



MEMOIRS OF THE XEW YORK BOTANICAL GARDEN 



stricted at the heterocysts under such circumstances. 



Growing with other species of Scytonema on rocks by the 

 road north of Maricao, no. 1253, type. 



Scytonema spirulinoides sp. nov. 



Plate 17, figure 37 



Filaments 500-800 n long, 15-20 \i diam., more or less fre- 

 quently curved and spirally coiled, forming a flocculent stratum; 

 trichomes 10-12 \i diam, at the apices, not constricted, much re- 

 duced in diameter in the older parts; cells cylindrical, one-half 

 to one-third as long as the diameter at the apices, quadrate in 

 the older parts, densely and finely granular; cross-walls indis- 

 tinct; heterocysts of the same shape and size as the cells, very 

 sparse ; branching very sparse ; sheath thick, homogeneous, dark 

 brown, rough on the margin. 



Growing on rocks along the road near San Lorenzo, no. 534, 

 type. 



This species is to be distinguished from others by the very 

 much distorted character of the filaments. Its nearest relative 

 possibly might be considered to be S. ocellatum. 



Scytonema tenellum sp. nov. 



Plate 18, figltre 38 



Filaments 200-300 m long, 12-16 n diam., flexuous and densely 

 intertwined, more or less erect, forming a thin, very dark stra- 

 tum, profusely branched; trichomes cylindrical, not tapering, 

 very slightly constricted at the dissepiments, 10-14 \\ diam. ; cells 

 one-half to one-fourth as long as the diameter, homogeneous, 

 pale aeruginous, cross-walls very thin but plainly visible ; hetero- 

 cysts numerous, golden yellow, of the same shape and size as the 

 cells, or in part almost cpiadrate; sheath thin, smooth, homo- 

 geneous, dark brown, close fitting; branching geminate, perpen- 

 dicular at first, soon gently curving. 



Growing on lava rock north of Sabana Grande, no. 936 a, 

 type. 



Scytonema javanicum (Kuetz.) Born. & Flali. has several 

 characters linking it with 8. tenellum. The latter is to be dis- 

 tinguished, however, by its very much shorter filaments, its 

 much more profuse branching, and its shorter cells. The 

 branches are much curved in various directions and frequently 



