412 Dr. J. E. Gray on the Arrangement of the Families 



in other allied Alga?, that each is contained in a distinct sac, 

 and that multiplication takes ])lace in the same way, by division 

 of the endochromc and formation of a new membrane round 

 each division." (Berkeley, Crypt.) 



* Filaments free, tvfted] erect. 



1. Calothrix. (C. confervicola, Harvey, Ph. Brit. t. 254.) 



** Filaments free, decumbent, simple. 



2. Lynghya. {L. majuscula, Harvey, Ph. Brit. t. 62.) 



3. Oscillatoria. (0. litoralis, Harvey, Ph. Brit. t. 105 a.) 



*** Filaments branched by apposition. 



4. Petalonema. (P. alatum, Hassall, t. 68. f. 6.) 



5. Scytonema. {S. myochrous, Hassall, 237. t. 68. f. 2.) 



**** Filaments bundled in a sheath. 



6. Microcoleus. [M. anguiformis, Harvey, Ph. Brit. t. 249.) 



7. Schizosiphon. [S. Warrenia, Harvey, Ph. Brit. t. 316.) 



***** Filaments radiating from a centre, and having a spherical cell 

 at the root. 



8. Rivularia. [R.plicata, Harvey, Ph. Brit. t. 315.) 



Fam. 2. NostochineaB. 



"The cells subglobular, increased by transverse and longitudinal 

 division. Threads very slender, moniliform, invested with gela- 

 tine, which is at length, to all appearance, common to the mass, 

 but at first appertains to each individual thread. Propagation 

 by division of the threads or by zoospores." (Berk. p. 139.) 



" The threads, broken up into fragments, burst through the 

 common envelope and become dispersed in the water; in this 

 condition they are endowed with spontaneous motion. These 

 fragmentary threads divide longitudinally and transversely, at 

 last constituting a bundle of new threads, which gradually, by 

 increase of the gelatinous or filamentous element, assume the 

 normal form of the species." (Berkeley, p. 140 ; see also Harvey, 

 Ner. Bor.-Amer. p. 111.) 



" It has been asserted that they are nothing but a state of 

 Lichens. It is true that the fronds of the Collcmal Lichens do 

 contain gonidia arranged in little necklaces ; but this appears to 

 be a mere case of analogy." (Berkeley, Crypt, p. 141.) 



a. Filaments invested in a mucous matrix forming a defined mass or frond, 



1. Nostoc, 



2. Monormia. {M. intricata, Hassall, 286. t. 7o. f. 11.) 



