NEW MYXOPHYCEAE FROM PORTO RICO 



89 



seriate, compressed-spherical, with distinct walls between and 

 protoplasmic conn(>ctions, about one-half as long- as broad, homo- 

 geneous, bright bhie-green; heterocysts formed by longitudinal 

 division of vegetative cells one-half of each becoming a hetero- 

 cyst; sheath smooth, firm, 2-2.5 m thick, homogeneous, dark 

 brown ; hormogonia secund, 45-60 n long. 



Growing on " Fly tteblok, " near Humacao, no. 573, type, and 

 no. 575 h; on rocks at Laguna Tortuguero, no. 852 d; on soil 

 along the road, Maricao, no. 1247; on bark by the road, north of 

 Maricao, no. 1261; on old plants on lava in a primeval forest, 

 near Hacienda Catalina, Palmer, nos. 768 a and 769. 



Stigonema elegans minus var. nov. 



Filaments sparsely branched, 1-1-1 On diam., trichomes 8.8^ 

 11 n diam. ; cells uniseriate, quadrate to one-half as long as the 

 diameter. 



Growing on rocks by the Arroyo de los Corchos, no. 1715 a, 

 type. 



The variety differs from the species in having smaller fila- 

 ments, smaller trichomes, and the cells averaging longer with 

 respect to the diameter. 



Stigonema congestum sp. nov. 



Plate 21, figure 52 



Filaments 150—22-") (j long, 12-15 \\ diam., very much con- 

 torted and intertwined, forming a thin, dense stratum ; branches 

 numerous, of 2 or 3 orders, all of similar diameters, slightly con- 

 stricted at the base, arising at right angles, but soon bending up- 

 ward ; cells uniseriate or when aged in part pluriseriate, closely 

 crowded, irregular in form, about one-half the diameter long, 

 homogeneous ; cross-walls thin ; tegument thin, firm, smooth, 

 homogeneous, dark brown; heterocysts fairly abundant. 



Growing on stones near Hacienda Catalina, Palmer, no. 791, 

 type ; on rocks near San Lorenzo, no. 503 ; in a stream about five 

 kilometers east of Coamo, no. 1886 e; on " Flytteblok, " west of 

 Humacao, nos. 570 a and 571 h; on red earth by the road. Haci- 

 enda Catalina, Palmer, no. 776 ; on red earth by the road north 

 of Maricao, no. 1241; on trunk of a palm tree at Santurce, no. 23 ; 

 on lava north of Sabana Grande, wo. 923 a and 936. 



