CHAPTER SEVEN 



THE GENUS MOUGEOTIOPSIS PALLA 1894 



These algae have simple filaments, with vegetative cells one- 

 half to four diameters long; each with a single quadrate, flat, or 

 dished platelike axile chromatophore with a thickened and mi- 

 nutely granulate margin. The margin is sometimes inroUed, and 

 pyrenoids are absent. Oil globules occur on the surface, and both 

 starch granules and oil drops within the chromatophores. Repro- 

 duction is by short to long ovoid zygospores irregularly formed 

 in the tube (isogamous) and extending into one or both gam- 

 etangia, but not cut off from the gametangia by a wall. Only one 

 species is known, from Europe and America. 



This genus has had an interesting history beginning with the 

 description and figures published by Palla (1894). In 1898 W. & 

 G. S. West claimed to have found the same alga with pyrenoids 

 and placed it in Debarya. In 1899 Brand described a new genus 

 from southern Bavaria which he called Mesogerrott. His descrip- 

 tion emphasized the dished or partly cup-shaped forms of the 

 chromatophore and the absence of pyrenoids. His figure exag- 

 gerates the curled edges of the chromatophores, as shown by an 

 examination of Brand's own specimens from Munich, which are 

 in my possession. Brand thought that his plant belonged among 

 the Ulotrichaceae, but Wille (1911) placed it provisionally among 

 the Zygnemataceae. Skuja reported the occurrence of Mesogerron 

 in Latvia in 1928, and in 1929 showed that "Mesogerron" is 

 merely the vegetative form of Mougeotiopsis. Although Czurda 

 (1932) insisted that the only important structure upon which 

 genera of the Zygnemataceae may be based is the chromatophore, 

 he includes this genus among the species of Mougeotia in spite of 

 the absence of pyrenoids, the presence of oil droplets, and the 

 unique thick-edged chromatophore entirely unlike that of any of 

 the known species of Mougeotia. It might be added further that 

 the zygospores, with their relatively thick and highly refractive 

 median walls with deep sharp-edged pits, are equally unique 



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