bearing body of the cell often takes the form of a close reticulum 

 and shows, therefore, much variation. See Fritsch (1929). 



Vegetative reproduction is by fragmentation. In sexual reproduc- 

 tion, unspecialized vegetative cells produce numerous globose eggs, 

 which at first are multinucleate. In the cells of other filaments, or 

 rarely in the same filament in which the eggs occur, numerous 

 spindle-shaped, biflagellate antherozoids are formed. Entrance is 

 effected by a small pore in the wall of the female gametangium. The 

 resulting zygotes are thick-walled and have decorated membranes. 

 They are capable of remaining dormant for several years, eventually 

 germinating to produce 1-8 biflagellate zoospores, from which new 

 filaments develop. 



The unique organization of the coenocytic cells, the form and 

 arrangement of the chloroplasts, and the method of sexual reproduc- 

 tion are characters which are here regarded as sufficiently dissimilar 

 from the Ulotrichales to warrant separation of Sphaeroplea from 

 that order. Although monogeneric orders make for an unwieldy 

 taxonomic system and are, therefore, to be avoided, there seems to 

 be no adequate justification for including Sphaeroplea in the Ulo- 

 trichales. Certainly it is consistent to regard the characteristics men- 

 tioned as criteria for segregation because they are fundamental and 

 are used to define other groups. 



FAMILY SPHAEROPLEACEAE 



SPHAEROPLEA C. A. Agardh 1824, p. XXV 



Free-floating filaments of long cylindrical multinucleate units 

 with thickened cross walls. Chloroplasts numerous, ovate, and so 

 grouped as to form up to 30 parietal bands or zones within each 'cell.' 

 Sexual reproduction oogamous; non-motile eggs and antherozoids 

 produced in unmodified vegetative 'cells' in the same or in separate 

 filaments. 



Sphaeroplea annulina (Roth) C. A. Agardh 1824, p. 76 



PI. 12, Figs 5-8 



Characteristics as described for the genus. Cells 27-72/a in diam- 

 eter, up to 20 times longer than wide. Spherical female gametes 

 arranged in a double series within unspecialized vegetative cells; 

 antherozoids numerous, fusiform, biflagellate bodies, usually pro- 

 duced in a separate filament. 



University Farm, Madison, Wisconsin (Gilbert), 



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