APPENDIX. 391 



saccate below, open (not fringed) above, forming a slippery 

 gelatinous frond. 



26. Euactis. Filaments whip-shaped, with repeated 

 ochreate sheaths, forming fronds in which they radiate, 

 and by superposition of successive generations form con- 

 centric layers ; the ochreate sheaths are cartilaginous, 

 lamellated, united laterally, funnel-shaped, fringed at open 

 edge. 



27. Inomeria. Filaments whip-shaped, vertical, paral- 

 lel ; obscure sheaths decomposed into slender filaments, 

 forming crustaceous fronds, becoming stony. 



28. Petronema. Densely csespitose, erect, somewhat 

 regularly branched ; branches free, with obtuse rounded 

 apices, and each with connecting cell at base ; filaments 

 annulated and growing thicker upwards. 



E. LEPTOTHRICE.E. Doubtful Oscillatoriacese. 



29. Leptothrix. Filaments very slender, neither articu- 

 lated, branched, concreted, nor sheathed. 



30. Hypheothrix. Filaments unbranched, inarticulate, 

 sheathed, interwoven in more or less compact stratum. 



31. Symploca. Filaments unbranched, sheathed, inar- 

 ticulate, concreted into branches, conjoined at their bases; 

 sheath a simple hyaline membrane. 



9. NOSTOCHACE,B. Gelatinous Fresh water, or in damp 

 mosses, etc. ; soft, or almost leathery, of variously curled 

 or twisted necklace-shaped filaments, colorless or green, 

 composed of simple (or double) rows of cells, contained in 

 a gelatinous matrix of definite form, or heaped without 

 order in a gelatinous mass. Some cells enlarge and form 

 vesicular empty cells or sporangial cells ; reproduce by 

 breaking up the filaments, and, by resting spores formed 

 singly in the sporanges. 



1. Nostoc. Phycoma, or general mass of plant in a film 

 formed by condensation of the surface ; globose, or spread 



