Clark — Holophi/tic Pla n lion of Lakes AtUla n and Amatitlan . 97 



color, about 4 mm. thick, obtained from the surface between pools of hot 

 water, Laguna, January 31. 



These filaments do not agree in every respect with any description that 

 could be found, but fit that of crucnta more closely than any other. On 

 account of the deviation from the description of that species the following 

 notes are appended : 



Filaments slender, 5-Sm in diameter, very light blue-green, with numer- 

 ous dark brown dots or granulations. No septa? visible ; most of the fila- 

 ments straight, but a great number gracefully undulate; apex bluntly 

 rounded ; no coiled forms were seen. 



In the jelly mass from which these filaments projected were numerous 

 filaments (Anabcrna stagnalisf) similar to those found in the Clathrocystis 

 colonies, but much longer, the filaments frequently attaining a length of 

 130/x. There were also present innumerable small cells, probably bacteria. 



8. Oscillaria chlorina Kuetzing. 



Oscillaria chlorina Kuetzing, Phyc. Germ. No. 10; Tab. Phyc, I, 28, 1845; 



Wolle, F. W. Alg. U. S., 311, 1887. 



I identify as this species examples collected by hand and not forming 

 part of the plankton proper. It formed a dirty green, somewhat firm 

 mass, looking much like a fresh-water sponge. Filaments 3m in diameter, 

 articulations indistinct, the cells about as long as wide. 



Order NOSTOCACEiE. 



9. Anabaena stagnalis Kuetzing. 



Anabxna stagnalis Kuetzing, Sp. Alg., 1849; Tab. Phyc. I, 50, Tab. 93, 

 fig. IV, 1845; Wolle, F. W. Alg. II. S., 288, 1887. 



Associated with Clatlirocystis colonies, as noted above, is a filamentous 

 form, which, after considerable study, I identify with Anabcena stagnalis 

 Kuetzing. It resembles in many respects some of Kuetzing' s figures of 

 species of Phormidium, but all which resemble it are much too large. I 

 have not observed any large heterocysts, which are said to be present in 

 A. stagnalis, but otherwise it fits the brief description of that species in 

 Wolle very well. The following notes were taken. 



Filaments short, straight, simple (one filament forked somewhat at the 

 end by ending in two diverging cells), usually about 2-8 cells long. Cells 

 usually somewhat elongate, sometimes spherical, turgid. Diameter of 

 filaments 3m; length of cells about 5m; length of long filaments about 

 20m, color very pale blue-green. Habitat, jelly of Clathrocystis colonies. 



In a jelly mass surrounding some Oscillaria found in one of the samples, 

 much longer filaments (attaining a length of 110m) of what appears to be 

 the same thing, are abundant. (See under Oscillaria cruenta.) It is 

 probable that the firmness of the Oscillaria jelly, as well as its freedom 

 from disturbance, permits a much longer growth of this form than in the 

 Clathrocystis. 



