10 ZYGNEMATACEAE 



sporiferous cells during aplanospore formation; no cytoplas- 

 mic residues 2. Zygnemopsis 



c) Zygospores unknown; 2-7 chromatophores in the cells; 

 aplanospores ellipsoid, on germination 1-3 sporelings develop 

 from each 3. Hallasia 



2. Chromatophores a pair of ovoid bodies with, or without, irreg- 

 ular processes, each containing a pyrenoid; zygospores in spo- 

 rangia of 2 cuplike parts with a suture between; aplanospores 

 and akinetes the usual method of reproduction; gametangia and 

 aplanosporangia contain cytoplasmic residues after conjugation 

 and spore formation 4. Zygogonium 



3. Chromatophores a pair of disc-shaped bodies each with a central 

 pyrenoid; sporangium wall of 2 cups with an equatorial belt 

 between them, otherwise similar to Zygogonium 



5. Pleurodiscus 



II. Vegetative cells, with single axile, platelike chromatophores with- 

 out pyrenoids; nucleus attached laterally near middle of the cell 



6. Mougeotiopsis 



III. Vegetative cells with i, rarely 2, axile, flat ribbonlike or plateUke 

 chromatophores, with several or many pyrenoids; nucleus attached 

 laterally or between the chromatophores when 2 are present 



1. Gametangia similar to the vegetative cells before the beginning 

 of conjugation 



a) During conjugation successive layers of pectic and cellulose 

 colloids are added to the inside of the gametangial walls, 

 filling the lumen; walls of sporangia similarly modified dur- 

 ing spore formation 7. Debarya 



b) During conjugation as the gametes contract and move to- 

 ward the conjugating tubes granular cytoplasmic residues 

 are left in the gametangia 8. Moitgeotia 



2. Gametangia are short specialized cells cut off near the ends of 

 long vegetative cells 9. Temnogameturyi 



IV. Vegetative cells with 2 parallel flat chromatophores on opposite 

 sides of the cell, each containing several pyrenoids; nucleus central 

 in a cytoplasmic pillar between the flat sides of the 2 chromato- 

 phores; conjugation between reflexed gametangia 



10. Sirocladium 



V. Vegetative cells with i or 2 broad parietal chromatophores on one 

 side of the cell, each with several pyrenoids, and laciniate lateral 

 margins; in young cells the nucleus is near the middle of the single 

 chromatophore, in mature cells in bridge between the 2 chroma- 

 tophores; reproduction unknown 11. Entransia 



