86 



MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



12-14 jj diam. ; cells cylindrical to slightly dolioform, quadrate to 

 3 times as long; sheath thin, hyaline ; heterocysts up to 50 [i long, 

 cylindrical. 



Growing among other filamentous algae and water plants, 

 not forming a definite stratum alone, in a water reservoir at Rio 

 Piedras, no. 118, type, and nos. Ill, 115, and 119 a ; along the 

 shore of Laguna Tortuguero, no. 843. 



The variety hrevis differs from the species in having shorter 

 filaments with the diameter averaging greater and with the cells 

 and heterocysts longer. No. 115 has mature cells averaging 38 

 to 45 \x long in the older parts of the trichome. 



Tolypothrix amoena sp. nov. 



Plate 20, figure 48 



Filaments 10-15 \i long, 22-26 n diam., densely interwoven 

 into a pannose stratum, very smooth and of equal diameter 

 throughout the entire length ; trichomes cylindrical, constricted 

 in part at the dissepiments, 16-18 \x diam., of the same diameter 

 throughout tlie entire length ; cells in part short cylindrical and 

 in part dolioform, one-third to one-fifth the diameter long, homo- 

 geneous or very finely granular, bright aeruginous, changing to 

 yellowish or greenish gray on drying; sheath very smooth and 

 straight, homogeneous, hyaline to slightly brownish ; heterocysts 

 ranging from almost cylindrical and longer than the diameter 

 through quadrate, spherical, to very much compressed, becom- 

 ing disk-shaped, prevailingly spherical, single or 2-5-seriate, 

 very numerous throughout the trichome ; branching sparse. 



Growing in a pool west of the Experiment Station, Rio Pied- 

 ras, no. 1932, type, and nos. 1935, 1936, 1941, 1943, 1945, and 

 1952; in a stream about five kilometers east of Coamo, no. 221 c. 



Tolypothrix amoena is a very distinct species, being very 

 definite in all of its characters. It has long, relatively straight 

 and rigid filaments. The sheath is firm, smooth, and homo- 

 geneous. In some parts of the trichome the heterocysts are 

 almost cylindrical, in others they are spherical and in still others 

 very much compressed, but always very distinct and conspicu- 

 ous. The cells are either perfect, short cylinders with no con- 

 strictions, or dolioform and conspicuously constricted. 



