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



plate. Each cell contains one nucleus and a central stellate 

 chloroplast with one pyrenoid. The cells, especially of young 

 plants, often divide in two or three directions. 



FAMILY I. PRASI0LACE.E. 



Coextensive with the order. 



Prasiola Ag. (inclus. Schizogonium Kiitz., and Hor- 

 midium Kiitz., in part). Found on moist earth, trunks of 

 trees, rocks, stones, etc. ; some species require very little 

 moisture. The cells of the filamentous thallus are broader than 

 long, and those of the flat plates quadrate or polygonal. The 

 cell walls are strong and colorless. Reproduction by gemmae, 

 by resting spores liberated at the margin of the thallus, and by 

 tetraspores. 



ORDER IV. C1EETOPHORALES. 



Thallus filamentous, simple or usually branched. Branches 

 generally attenuated and bearing long hairs. The uninucleate 

 cells possess each, except in Trentepohliacccv, a single parietal 

 chloroplast with one or more pyrenoids. Asexual reproduction 

 by resting spores or zoogonidia with two cilia. Sexual repro- 

 duction by isogamous planogametes with two cilia, or by 

 heterogamous gametes. 



Key to Families. 



i. Plant entirely filamentous, simple 2 



Plant of branched filaments forming a flat cushion- 

 like expansion enveloped in mucilage 



COLEOCHJETACE.^ 



2. Filaments branched 3 



Filaments not branched 5 



3. Gametes arise from special cells only 



TRENTEPOHLIACE.E 



Gametes arise from any cell of the filament 4 



4. Small creeping filaments upon water plants; cells 



globose or cylindrical herposteirace^e 



Like the above, but with flask-shaped cells 



chjetosph^eridiace.e 

 Plant not creeping ch.etophorace^e 



