Key to the Genera 



Inhabiting the tissues of Lemna Chlorochytrium 



Free-Hving or embedded in the mucilage of other algae Kentrosphaera 



CHLOROCHYTRIUM Cohn 1875, p. 102 

 Unicellular, oblong or broadly ellipsoid, often irregular in outline, 

 formed when a zygote germinates and sends a tubular elongation 

 into the tissues of Lemna, the cell contents migrating into the tube 

 and then enlarging among the host cells, the entrance tube persisting 

 as a knob-like extension of the wall, which is thick and lamellate; 

 chloroplast at first parietal, later becoming radial and massive; 

 reproduction by division of the cell contents into a large number of 

 biflagellate isogametes or zoospores. 



Chlorochytrium Lemnae Cohn 1875, p. 102 

 PI. 45, Figs. 6, 7 

 See characters of the genus; cells broadly ellipsoid or ovate, with 

 1 or more knob-hke extensions; wall thick and lamellate; cells 60- 

 100/i, in diameter, inhabiting the tissues of Lemna trisulca. 



In host plants collected from water of marshy lakes; in roadside 

 swamps. Mich., Wis. 



KENTROSPHAERA Borzi 1883, p. 87 



Unicellular, often crowded and intermingled with other algae, 

 sometimes living in the mucilage of colonial Myxophyceae; cells 

 irregularly ovate, ellipsoid, or sub-cylindric; walls lamellated, irreg- 

 ularly thickened with knob-like outgrowths; chloroplast axial, with 

 extensions flattened at the wall to form irregularly shaped processes; 

 one pyrenoid. 



Kentrosplmera gloeophila ( Bohlin ) Brunnthaler 1915, p. 68 



PI. 45, Figs. 8-10 

 Characters of the genus; cells broadly ovate, or ovoid or elliptic, 

 with knob-like thickenings of the lamellate wall, 18-20/x in diameter, 

 25-30/A long. 



(For a discussion of the nomenclature of this species see Moore, 

 1917; G. M. Smith, 1933; Bristol, 1920.) 

 Among thick clots of blue-green algae. Wis. 



FAMILY CHARACIACEAE 



This is a small family of which there is but a single genus 

 ( Characium ) represented in our collections. ( Actidesmium, reported 

 from California and arctic Alaska, has spindle-shaped, free-floating 



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