62 



MEMOIRS OF THE KEW YORK BOTANICAL GARDEN 



as the diameter, terminal cell conical ; heterocysts doliof orm, 5 p 

 diam., 8-10 n long; spores single or in pairs, and contiguous to 

 the heterocysts on both sides, elliijsoidal, about 10 n diam. and 

 20 [1 long, with smooth hyaline walls. 



Growing in a ditch near Mayagiiez, no. 1004, type; on plants 

 in a pool between Hatillo and Arecibo, no. 1355. 



Anabaena portoricensis sp. nov. 



Plate 12, figure 1-4 



Trichomes 7-8 \x diam. ; cells dolioform to compressed-spher- 

 ical, pale aeruginous; apical cells subsi^herical to blunt-conical, 

 usually smaller than the others of the trichome; heterocysts 

 spherical, 10 \x diam. ; spores broadly ellipsoidal, 10 n diam., 

 about 15 \x long, contiguous to the heterocysts. 



Growing in a ditch near Ponce, no. 1670 h, type. 



Nostoc Willei sp. nov. 



Thallus iregular in shape and size, tirm, gelatinous, 1-4 mm. 

 diam.; trichomes moderately contorted; cells cylindrical to 

 slightly dolioform, 3.7-4 \\ diam., slightly constricted at the dis- 

 sepiments, up to 18 M long, densely and finely granular ; hetero- 

 cysts spherical, 5-5.5 n diam., smooth and hyaline ; teguments 

 hyaline; resting spores subcylindrical to ellipsoidal, 14^20 n 

 long, 7-9 M broad, with a smooth hyaline membrane. 



Growing among moss on trunks of trees at Coamo Springs, 

 no. 267, type. 



This species of Nostoc belongs to the Humifusa section of 

 the genus created by Bornet and Flahault and is related in the 

 trichome characters to N. eUipsosporum (Desm.) Rab. 



Nostoc Brittonii sp. nov. 



Thallus spherical, up to 2 mm. diam., firm, smooth ; trichomes 

 very tortuous, moderately crowded, 3.6-4.8 n diam. ; cells dolio- 

 form to subspherical, bright violet or drab, fading to greenish ; 

 heterocysts siiherical, single in the juvenile stage of the tri- 

 chome, later, on the formation of hormogonia, two or more are 

 formed, these usually being somewhat smaller; tegument opales- 

 cent when young, changing to purplish drab, and finally to yel- 

 lowish brown ; resting spores unknown. 



At "Campo" south of Marieao, collected by Dr. N. L. Brit- 

 ton, no. 1290 a, type; collected by Dr. Wille in the same locality, 

 no. 1229 c. 



