12 



AQUATIC PHYCOMYCETES 



Further details of the structure of the flagella of the primary and 

 secondary zoospores of Saprolegnia have been given by Manton, et ol. 

 (1951,1 952). Those investigators found that the anteriorly directed flagel- 

 lum in both the primary and secondary spores has tinsel hairs arranged 

 in two rows, each hair ending in a thin delicate point. The fibrillar axis 

 is covered by a wide transparent sheath and a similar sheath surrounds 

 that of the fibrillar axis of the smooth, whiplash posterior flagellum. 



Fig. 2. Flagellar types 



A-G. Zoospores of the Chytridiales, Monoblepharidales, and Blastocla- 

 diales; stained to show whiplash type of posterior flagellum. H. Zoospore 

 of Rhizidiomyces showing tinsel type of anterior flagellum of Hyphochytriales. 

 /. Primary zoospore of Saprolegniales, showing anterior tinsel and posterior 

 whiplash flagella. J-K. Biflagellate secondary zoospore of Lagenidium and 

 Olpidiopsis of the Lagenidiales, showing anterior tinsel and posterior whip- 

 lash flagella. L. Biflagellate zoospore of Plasmodiophorales showing flagella, 

 both of the whiplash type. M. Biflagellate secondary zoospore of Achlya. 



(From Couch, 1941; Koch, 1951; and Goldie-Smith, 1954). 



Both types of flagella disintegrate into eleven fibrillar strands, but in 

 the posterior one, which dismembers less easily, there are clear indi- 

 cations, as in Allomyces, of a transverse cementing material. These 

 authors interpret the massive sheath surrounding the fibrillar axis as 

 a homogeneous secretion rather than a tubular structure. There is 

 some evidence for believing that the sheath, at least in the posterior 



