34 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



Palmellococcus Chodat (Protococcus Ag., in part). 

 Strictly unicellular Algae, globose, green, sometimes changing 

 to red upon exposure. Cells formed singly or in clusters, 

 growing in water, or on damp soil, flower-pots, trunks of trees, 

 etc. ; 8, 16, 32, or 64 spores formed within a mother-cell, the 

 wall of which ruptures and sets them free. Very rapid multi- 

 plication by cell division. 



P.sp. (?), Fig. 30. 



P. Gigas (Kutz.), Fig. 31. 



SUB-FAMILY IV. SELENASTRE^. 



Cells elongated and attenuated, sometimes lunate ; solitary, 

 or joined into fragile families. A single chloroplast, which 

 may contain one or many pyrenoids, is found in each cell. 

 The cell wall is delicate but firm. Multiplication by autospores 

 or autocolonies. 



Key to Genera. 



1. Colonies enveloped in mucus Kir c line riclla* 



Colonies almost destitute of mucus 2 



2. Cells attenuated to acute apices 3 



Cells sublunate or ellipsoidal, arranged in groups of 



four in a plane ; groups forming irregular colonies 



Dimorphococcus 



3. Cells forming definite colonies of a row of cells in one 



plane Sccnodesmus* 



Cells solitary or loosely grouped in irregular bundles 



A nkistrodesmus* 



Cells lunate, arranged back to back Selenastrum* 



Cells dividing, oblique ; daughter-cells remaining at- 

 tached loosely by their apices Dactylococcus 



Description of Genera. 



Kirchneriella. The cells are bent like a bow, often until 

 their apices almost touch each other ; loosely aggregated within 

 an enveloping mass of jelly. The cell wall is thin, the chloro- 

 plast parietal ; multiplication by autospores, four or eight of 

 which are produced in a mother-cell. The genus differs from 

 Selenastrum in the presence of jelly. 



K. obesa (West) Schmidle, Fig. 54. 



