ASTEROTHRIX. 323 



A peculiar form, seems fitly placed with this genus, 

 although unlike any of the three species named by Raben- 

 horst. For the establishment of a good species corrobora- 

 tive specimens are desirable. 



Plate CCIX, figs. 22-25, filaments in their normal appear- 

 ance under a magnification of 500 diameters. 



ASTEROTHRIX PERTYANA, Naeg. 



A form much larger than the preceding and otherwise 

 distinct, is described by Naegeli, found with Confervae in 

 Switzerland. The figure is transcribed to close a vacant 

 part of Plate CCIX, figs. 20, 21. 



Genus 106, SPIRULINA, Link. 



Trichomes articulated, spirally twisted, more or less motile, 

 OsciUaria-\ike, usually surrounded by a somewhat liquid, color- 

 less mucilage. 



SPIRULINA JENNERI, Kg. 



Trichomes solitary or in interwoven masses, distinctly 

 articulated, spirals lax, a turn occurring in every 20-24 /< ; 

 cells about as long as wide ; color light or darker aeruginous. 



Diameter of trichomes, 7-8 yw. 



Syn. Spirillum Jenneri, Hass. ; Arthrospira Jenneri, Hedw. 

 In stagnant waters, usually only solitary filaments. 

 Plate CCX, fig. 2, two short parts of trichomes. 



SPIRULINA TENUISSIMA, Kg. 



Trichomes very thin ; flexuous, densely or more loosely 

 spiral, endowed with active motion, joints indistinct, form- 

 ing a lubricous stratum, light aeruginous, on the bottom of 

 warm sulphur springs. 



Diameter of spirals, 4-5 yw, making 5-7 turns in space 

 of 25 A/. 



If not strictly identical in every particular with the Euro- 

 pean forms described under this name, our plant is very 

 near to it, and entirely unlike all others. 



Frequent in sulphur springs, Clifton, New York, and Glen 

 Cove Springs, Florida. 



Plate CCX, fig. 3. 



SPIRULINA DUPLEX, Wolle. 



Trichome a slender, flat, strap-like, continuous band. 

 When untwisted forms a complete ring. Normally it is 



