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

 

XANTHIDIUM

Unicellular Desmid: semicells dorsoventrally flattened without lateral incisions, with marginal spines and a central process.
 
 
 
Xanthidium antilopaeum  
 
Xanthidium antilopaeum v. depauperatum  
 
     
Xanthidium antilopaeum v. hebridarum  
 
Xanthidium armatum  
 

     

Xanthidium cristatum  
 
Xanthidium octocorne  
 
Xanthidium subhastiferum  
       

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Saccoderm:      

John Kinross
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