58 



MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



closed at the apices when young, later the ends dissolving and 

 the triehonies extruding; trichomes nearly parallel, separated 

 from each other for the most part, moderately constricted at 

 the dissepiments, acuminate at the apices; cells homogeneous, 

 pale to bright aeruginous; cross-walls very thin; apical cell 

 blunt-conical, with a very small calyptra ; sheath ample, hyaline 

 when young, changing to pinkish red at maturity, homogeneous. 



Growing on clay soil among other Myxophyceae, together 

 forming a very thin, compact stratum, Experiment Station, May- 

 agiiez, no. 972, type. 



The organism described here is one of many in the collection 

 which hover around the generic borders. The filaments are 

 small for the genus Hydrocoleum and lack the characteristic well- 

 developed calyptra or thickened end wall of the typical species 

 of that genus. Its colored sheath and small number of trichomes 

 within a sheath do not well coincide with typical members of 

 the genus Microcoleus. Its unbranelied filaments combined with 

 its colored sheath and prostrate habit do not unmistakably ally 

 it with any of the Schizothrix group. 



The material is mature and most of the trichomes separated 

 more or less into hormogonia, hence characteristic attenuated 

 and cajDitate ends are very sparse. 



Anabaena lutea sp. nov. 



Plate 12, figure 7 



Trichomes densely aggregated, moderately straight, 4.8-5.2 n 

 diam., deeply constricted ; cells subcylindrical to dolioform, about 

 2 times as long as the diameter, homogeneous, pale drab to 

 amber-colored, forming microscopic colonies irregular in shape 

 and size, but mostly membranaceous ; heterocysts spherical, sub- 

 spherical to dolioform; 6.5-7.5 m diam; spores dolioform to 

 broadly ellipsoidal, 7-8 n diam., 12-15 p long, wall smooth, 10-15- 

 catenate ; tegument yellowish or amber-colored at maturity, 

 moderately firm. 



Growing on earth about five kilometers south of Adjuntas, 

 no. 16G5, type; in a small stream about five kilometers east of 

 Coamo, no. 237 c. 



It is somewhat difficult to determine the generic jjosition of 

 the organisms described above. It is not unlike some of the more 

 or less foliaceous species of Nostoc, forming colonies with a 



