64 



MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



Nostoc membranaceum sp. nov. 



Tliallus in the juvenile stage more or less spherical and solid, 

 soon becoming hollow, still later becoming much lacerated and 

 expanding into thin, membranaceous, somewhat papery, strata 

 5-8 cm. across, 100-125 n thick ; trichomes tortuous, densly 

 packed together; cells spherical to compressed-spherical, 4.6- 

 5.2 M diam., pale aeruginous, almost homogeneous, but at times 

 containing a few small granules ; heterocysts spherical, 5.8-6.4 n 

 diam., very numerous; tegument firm, smooth on the outside, 

 hyaline or changing to yellowish brown with age; resting spores 

 unknown. 



Growing on sand rock along the shore of the Rio Grande, 

 near Sabana Grande, no. .942, type; on a water pipe near a 

 stream in the vicinity of Maricao, no. 1147. 



Nostoc sphaerosporum sp. nov. 



Thallus spherical or in part irregular in form when young, 

 becoming more irregular with age ; up to 600 n diam. ; trichomes 

 moderately flexuous and intricate, not densely crow^ded, becom- 

 ing straigiiter when spore formation begins, 3-3.6 n diam., pale 

 aeruginous; heterocysts spherical, 6-6.5 n diam., hyaline; spores 

 spherical, 4.7-5.5 n diam., smooth, hyaline ; tegument dirty white, 

 moderately firm. 



Growing on bark among other Myxophyceae near Utuado, no. 

 1506 a, type. 



The diminutive size of the colonies coupled with the spherical 

 spores, heterocysts, and cells, constitute a combination of char- 

 acters distinctive of this species, 



Nostoc ellipsoideum sp. nov. 



Thallus without definite form, usually flattened and irregular, 

 firm-gelatinous or cartilaginous up to 3 mm, diam. ; trichomes 

 moderately tortuous, not densely congested, pale aeruginous, 

 deeply constricted at the dissepiments; cells cylindrical to nar- 

 rowly ellipsoidal, 1.4-1.8 |j diam., quadrate to 2.2 times as long 

 as the diameter, homogeneous; heterocysts dolioform, 2.4-2.8 n 

 diam.; spores ellipsoidal, about 3 n diam., about 6 m long; tegu- 

 ment opalescent, changing to yellowish brown at maturity. 

 Growing on rocks in the vicinity of Jayuya, no. 1797, type, 

 Nostoc ellipsoideum appears to have its nearest affinities in 

 Humifusa section of the genus. The spores seem not to be quite 

 mature. 



