7. Cells solitary or in colonies of definite or indefinite shape; cells 

 variable in form ( spherical, ovate, lunate, polyhedral, etc. ) , 

 not adjoined to one another; reproduction by autospores oocystaceae 



7. Two to eight cells adjoined together or adherent to form 

 a pattern of definite shape ( a linear series, stellate, or 

 cruciate ) ; reproduction by the formation of autocolonies 

 within the cells of the parent coenobium scenedesmaceae 



FAMILY CHLOROCOCCACEAE 



In this family the cells vary in shape from spherical to fusiform or 

 spindle-shaped (represented in our collections by spherical cells 

 only ) , The family is characterized by the use of zoospores in asexual 

 reproduction. These escape through a pore in the wall and separate 

 immediately. In some forms arrested zoospores ( aplanospores ) may 

 function. 



The plants are mostly solitary and free-floating, but in one genus 

 (Chlorococcum) cells are gregarious and sedentary, inhabiting 

 moist soil or other subaerial habitats. The cell wall may be smooth 

 or spiniferous. There is considerable variation in the form of the 

 chloroplast which may be a parietal or massive cup, or axial and 

 stellate, with I or more pyrenoids. In some species the cells become 

 much enlarged and in age multinucleate. 



In the identification of members of this family a comparison should 

 be made with similarly shaped plants in the Oocystaceae. 



Key to the Genera 



1. Cells spherical or subspherical, inclosed in a wide, 



longitudinally striated, spindle-shaped sheath Desmatractum 



1. Cells spherical, not inclosed in a sheath 2 



2. Cells free-floating, soUtary, the walls setiferous 3 



2. Cells sedentary, or rarely free-floating, sohtary or gregarious on 



moist earth or submerged substrates; wall smooth Chlorococcum 



3. Setae gradually tapering from the base to apex Golenkinia 



3. Setae thickened for a short distance in the basal portion, 



then abruptly narrowed and tapering to apex Acanthosphaera 



CHLOROCOCCUM Fries 1825, p. 356 

 Cells spherical, solitary or more often gregarious in amorphous 

 gelatinous clumps, or forming films on moist or submerged sub- 

 strates; cell wall thin and undecorated; chloroplast a thin parietal 

 plate covering the wall or nearly so, containing 1 pyrenoid; repro- 

 duction by 8-16 oblong zoospores with 2 flagella. 



Species of Chlorococcum should be compared with Chlorella. See 

 note under that genus. 



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