SCHIZOPHVTA. 25 



Order 3. Chamaesiphonaceae. The individuals are 1- 

 many-celled, attached, unbranched filaments with differentiation 

 into apex and base, without heterocysts. Multiplication by re- 

 productive akinetes; resting akinetes are wanting. Dermocarpa, 

 Clastidium, Chamcesiphon, Godlewskia, Phragmonema. 



Order 4. Nostocaceae. The individuals are formed of mul- 

 ticellular, unbranched filaments, without differentiation into apex 

 and base ; heterocysts present. Reproduction by synakinetes and 

 resting akinetes. 



Some genera are not mucilaginous, e.g. Cylindrospermum (Fig. 

 19). The cell-chains in others, e.g. Nostoc, wind in between one 



FIG. 22. Nostoc verrucostim. A The plant in its natural size ; an irregularly folded 

 jelly-like mass. B One of the cell-chains enlarged, with its heterocysts (ft), embedded in 

 its mucilaginous sheath. 



another and are embedded in large structureless jelly-like masses, 

 which may attain the size of a plum or even larger (Fig. 22) ; 

 sometimes they are found floating in the water, sometimes 

 attached to other bodies. Other genera as follows : Aphanizo- 

 menon and Anabc&na (in lakes and smaller pieces of water) ; 

 Nodularia is partly pelagic. Some occur in the intercellular 

 spaces of higher plants, thus Nostuc-forms are found in Anthocerus, 

 Blasia, Sphagnum, Lemna, and in the roots of Cijcas and Gunnera ; 

 Anabvena in Azolla. 



Order 5. Rivulariaceae. The individuals are multicellnlar 

 filaments, with differentiation into apex and base ; spurious 

 branching, and a heterocyst at the base of each filament. Re- 

 production by synakinetes and resting akinetes, rarely by simple 

 reproductive akinetes. Rivulama, Glceotrichia, Isactis, Caluthrix. 



Order 6. Scytonemaceae. The individuals are formed of 

 mnlticellular filaments with no longitudinal division ; differen- 

 tiation into apex and base very slight or altogether absent ; 



