HOW TO KNOW THE FRESH-WATER ALGAE 

 179b Cells without longitudinal ribs 180 



180a Cells small, less than 4.5 ,l long, with a plate-like chloroplast at 

 one end. See Fig. 116 NANNOCHLOR1S 



180b Cells relatively large, without such a chloroplast 181 



181a Two or more masses of dark mucilage appearing at either end or 

 on either side of the cell; usually 2-4 cells in a common invest- 

 ment, but often solitary. See Fig. 83 GLOEOTAENIUM 



181b Without dark masses of mucilage about the cells 182 



182a Cells oval, often solitary but usually gregarious, forming an ex- 

 panse on moist aerial substrates. See Fig. 125 



PALMELLOCOCCUS 



182b Cells lemon-shaped oval or ellipsoid (usually several together in 

 old mother-cell wall, but may occur solitary); aquatic. See Fig. 

 85 OOCYSTIS 



183a (155) Cell body actually spherical but with 4 long, narrow, brown 

 arm-like appendages radiating from it. Fig. 128. PACHYCLADON 



Fig. 128. Pachycladon umbrinus G. M. Smith. 

 (Redrawn from Smith.) 



This rare plant (one species in the genus) oc- 

 curs in the euplankton of lakes. The long, dark- 

 ly colored appendanges from a relatively small, 

 subspherical cell body make it easy of identifi- 

 cation. 



Figure 128 



85 



