DESMIDS

Phylum Chlorophyta; sub-phylum Chlorophyceae; Order Zygnematales

There are two groups of Desmids: the "Placoderm" and the "Saccoderm" Desmids.

Placoderm desmids have cells composed of two halves (semicells), often almost divided from each other by deep median incisions. The cells are symmetrical about 3 planes, and often bear elaborate ornamentation. Genera are Cosmarium, Cosmocladium, Euastrum, Micrasterias, Staurastrum, Staurodesmus, Xanthidium.

Saccoderm desmids are simple shapes, cylindrical or spindle-shaped, rarely with any median constriction. This group forms the family Mesotaeniaceae and includes the genera Cylindrocystis, Mesotaenium, Netrium, Roya, Spirotaenia, Tortitaenia, and, in the suborder Closteriinae, Closterium, Gonatozygon and Penium, and in the suborder Desmidiinae, Actinotaenium.

             
Saccoderm:

ILLUSTRATIONS:

Placoderm

 

 

MICRASTERIAS


Unicellular Desmid, forming a flat plate: semicells are divided by several deep incisions.
 
 
Micrasterias americana  
 
 
Micrasterias crux-melitensis  
 
       
Micrasterias fimbriata
 
 
 
Micrasterias jenneri  
 
  
Micrasterias papillifera  
 
Micrasterias pinnatifida  
 
   
Micrasterias radiosa  
 
   
Micrasterias rotata  
 
   
Micrasterias thomasiana v. notata  
 
Micrasterias truncata  

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Saccoderm:

John Kinross
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