FAMILY OOCYSTACEAE 



This is a large family in which there is a wide range in cell shape 

 and arrangement. The cells may be spherical, ovate, pyramidal, or 

 polygonal. Some forms are unicellular, others colonial. The chief 

 characteristic which unites the 30 or more genera is the autospore 

 method of reproduction; ordinary cell division and zoospore for- 

 mation are not known. The autospores are small replicas of the 

 mother cell and are usually cut out in a definite number from the 

 parent protoplast. Upon escape they may remain together to form 

 a colony, as in the Coelastraceae, or may separate. Unlike the 

 Coelastraceae and the Scenedesmaceae, however, the colonies are 

 not composed of definitely arranged cells. In most cases the cells 

 are not adjoined but are held together by a gelatinous investment 

 or by the enlarged and persistent mother cell wall, or gelatinized 

 portions of the old wall. In the majority of forms there is a single, 

 laminate chloroplast, but a few species have several to many disc- 

 like bodies, each with a pyrenoid. Multinucleate cells are rare. 



Key to the Genera 



1. Plants endozoic in the cell or body cavities of animals 



( sponges, Hydra, etc. ) Zoochlorella 



1. Plants not endozoic 2 



2. Plants unicellular 3 



2. Plants colonial _ 21 



3. Cells angular, pyramidal, triangular, or polygonal 4 



3. Cells spherical, ellipsoid, ovoid, or acicular 8 



4. Angles bearing spines or bristles 6 



4. Angles not bearing spines; smooth or with the angles produced 



and extended to form simple or branched processes 5 



5. Cell body evident, distinguishable from the extensions of the 



angles, or with angles smooth and rounded Tetraedron (part) 



5. Cell body not clearly evident, gradually extended into the 



processes of the angles Cerasterias (^part) 



6. Body of the cell evident, with or without 



produced angles 32 



6. Body of the cell not clearly evident, gradually extended into the processes . 7 



7. Angles of the cell with a thick, stout, and very long spine Treubaria 



7. Angles of the cells gradually narrowed to form a spine-like tip, 



or with the apices tipped with minute spines Cerasterias (part) 



8. Cells spherical - 9 



8. Cells ovate, ellipsoid, lunate, or acicular 14 



9. Cell wall smooth -10 



9. Cell wall not smooth , 13 



10. Cells with 1 chloroplast (see also Zoochlorella) Chlorella 



10. Cells with several to many chloroplasts 11 



11. Cells inclosed by a wide gelatinous investment; chloroplasts not 



in a reticulum nor in radiating strands Planktosphaeria (part) 



11. Cells not inclosed by a gelatinous investment 12 



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