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

 

 

STAURODESMUS


Unicellular Desmid: semicells have a smooth appearance, with spines marginal, or at the angles.
 
 
Staurodesmus aversus  
 
    
Staurodesmus convergens biradiate  
 
   
Staurodesmus cuspidatus  
 

?    

Staurodesmus dejectus  
 
   
Staurodesmus dejectus fo. apiculatus  
 
 
Staurodesmus ? extensus  
 
Staurodesmus ? indentatus  
 
   
Staurodesmus mammilatus  
 
 
Staurodesmus ? megacanthus  
 

   

   

Staurodesmus subtriangularis  
 
   
Staurodesmus triangularis  

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Saccoderm:      

John Kinross
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