OSCILLATORIACEiE. 287 



pools, near high-water mark. It may be distinguished 

 by its comparatively large size and variegated threads. 



Genus CXIX. OSCILLATOBIA. 



Fronds simple, rigid, needle-like threads developed in 

 and radiating from a gelatinous matrix, vividly oscillating ; 

 tube continuous, filled with densely annulated, greeu eudo- 

 chrome. — Oscillatoeia, from the Latin oscillum, a swing- 

 ing motion. 



Most of the species belonging to this genus grow in 

 fresh water ; but some few are marine. Their most re- 

 markable character is the oscillating, pendulum-like mo- 

 tion of the threads ; this is more distinctly visible in 

 some species than in others, and is alway greater in warm 

 weather than in cold. 



Oscillatoria litoralis. The shore Oscillatoria. 



Threads thick, variously curved, growing in a bright 

 verdigris-green layer ; endochrome distinctly marked with 

 closely set striae, " divided at uncertain intervals into por- 

 tions, which probably break off eventually and become new 

 filaments." 



This species was first found by Captain CarmichaeL, 

 in muddy pools near the seashore, at Appin. Kiitzing 

 considers it to be identical with Lyngbya crispa of 

 Agardh. 



Oscillatoria spiralis. The spiral Oscillatoria. 



Threads slender, very short, much twisted, or spiral, 

 closely interwoven, growing in dark or bluish-green, more 

 or less leathery layers of indefinite dimensions ; endochrome 

 marked with somewhat distant, indistinct striae. 



