CHAPTER NINE 



THE GENUS MOUGEOTIA C. A. AGARDH 1824 



Plants belonging to this genus were figured and described as 

 early as 1803 by Vaucher in his Histoire des Conferees. Agardh, 

 however, was the first to classify these plants in a way that clearly 

 distinguished them from other "conjugates." During succeeding 

 years of the nineteenth century there was much confusion about 

 the nature of the group of cells now called the spore, sporangium, 

 and the gametangia. Some authors interpreted the group of cells 

 as the spore; others thought the gametangia and conjugating tube 

 constituted a "carpogonium." When the gametangia became 

 divided by the sporangium walls, the ends of the gametangia were 

 looked upon as "sterile cells," since they are not empty but contain 

 "cytoplasmic residues." Hence, many descriptions until those of 

 very recent years contain the statement that the spore, or "fertile 

 cell," is adjoined by two, three, or four "cells" instead of two, 

 three, or four dead ends of the gametangia. Apparently, because 

 of the "residues," many authors could not see the complete homol- 

 ogy between these reproductive structures and those of Zygnema. 



Because of the emphasis placed on the reproductive structures, 

 the position of the "fertile cell" relative to the remnants of the 

 gametangia became the basis of several genera which have been 

 discarded by most authors. These generic names are only of 

 historic interest and are listed at the end of the section. Plants of 

 this genus are generally simple filaments of cylindric cells. Rarely 

 one celled or two celled branches occur, particularly near the bases 

 of filaments where the latter are anchored by coiling around a 

 support or are attached to some substrate by rhizoids. 



The vegetative cells are comparatively long, five to twenty 

 diameters, with plane end walls that are thinnest at the center. 

 Hence when the cells of a filament separate, the free ends are 

 usually somewhat conical. Each cell has one or two axial, flat 

 chromatophores extending the full length of young cells but 



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