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:

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Saccoderm: Closteriinae

Closteriiniae:Closterium
unicellular Desmid, varying from crescent shaped to straight:
radius of curvature, dimensions and wall ornamentation distinguish species
Closterium ?abruptum
 
Closterium acerosum
 

Closterium aciculare


Closterium angustatum
   
 
Closterium attenuatum
   
Closterium baillyanum
   
Closterium closterioides
 
Closterium cornu
     
   
Closterium costatum
 
 
 
   
Closterium dianae
   
 
Closterium dianae v. minus
   
 
Closterium dianae v. pseudodianae
 
 
 
Closterium directum
     
 
Closterium ehrenbergii  
      
Closterium gracile
 
Closterium gracillimum
 
 
Closterium idiosporum
 
Closterium incurvum
     
 
Closterium intermedium
 
Closterium jenneri
     
 
Closterium juncidum
   
?Closterium juncidum v. elongatum
         
Closterium kutzingii
     
Closterium lebleinii
 
Closterium littorale
     
   
Closterium lunula
   
         
Closterium moniliferum
       
Closterium navicula
     
Closterium ? parvulum
   
Closterium praelongum

 
Closterium ralfsii 
   
Closterium setaceum
      
Closterium striolatum
 
Closterium venus

Closteriiniae
: Gonatozygon


Filamentous Desmid: elongated cells usually in pairs joined end-to-end, ends slightly swollen, cell surface decorated, chloroplast axile.


Gonatozygon kinahanii
   
Gonatozygon monotaenium

Closteriiniae
: Penium

Unicellular Placoderm Desmid: cylindrical with rounded ends, cell wall granular, 1 chloroplast in each semicell (sometimes interrupted in P. margaritaceum).
Penium exiguum
Penium margaritaceum
   


             
Saccoderm:


John Kinross
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