OSCILLATOKIACE^. 283 



which causes the filaments p3 radiate, and spread out 

 from the edge of the stratum. If a minute portion of a 

 living Oscillatoria be placed in water under a moderately 

 high magnifying power, all these movements can be 

 seen without trouble." These facts relate rather to the 

 freshwater than to the marine species with which alone I 

 am at present concerned, but they are so interesting in 

 themselves that I could not refrain from recording them. 

 I may add, that some species of Oscillatoria is to be 

 found floating like a black or green scum on nearly every 

 pool of stagnant water. 



Genus CXVII. LYNGBYA. 



Frond a simple, free, flexible, stationary, non-mucila- 

 ginous thread, composed of a continuous, cylindrical, mem- 

 branaceous tube, filled with green or purple endochrome, 

 which is densely annulated, and from which leus-shaped 

 sporidia are developed. — Ltngbta, in honour of H. C. 

 Lyngbye, a Danish algologist. 



Some of the species belonging to this genus are ma- 

 rine, and others grow in brackish or in fresh water. 

 They are distinguished from the Calothrices by the 

 greater length of their threads, and by their general 

 habit, and from the Oscillatorits by the absence of a 

 gelatinous matrix and of oscillating movement. 



Lyngbya majuscula. The large Lyngbya. 



Threads robust, tough, hair-like, twisted, growing in 

 large tufts, which are densely interwoven in the centre, at 

 first attached to the substance on which they grow, then 

 floating ; tube thick, forming a wide, transparent border 

 to the dark-coloured endochrome. 



This species grows on mud or sand, among rocks, 



