INTRODUCTION 9 



diales (Fig. 1 A-B, p. 8) the body of the spore is usually, but not 

 always, radially symmetrical, and in most species contains a highly 

 refractive "oil globule" and, sometimes, minute granules as well. The 

 posterior flagellum may vary in length, depending upon the species, 

 but is at least twice the diameter of the body and usually longer. In 

 the Blastocladiales (Fig. 1 B-C), the body tends to be bilaterally sym- 

 metrical and lacks the conspicuous globule of the chytrid spore. There 

 is, moreover, a somewhat central, hemispherical nuclear cap frequently 

 visible, and sometimes (but usually only to be seen after staining) a 

 tear-shaped "side body." The flagellum is always quite long. The Mon- 

 oblepharidales (Fig. 1 C-D) also possess a posteriorly uniflagellate 

 type of zoospore which, while it lacks a globule as does that of the Blas- 

 tocladiales, usually has an anterior granule or collection of granules 

 which projects forward as the spore is in motion. 



2. The anteriorly uniflagellate zoospore that is found in the few fungi 

 making up the Hyphochytriales (Fig. 1 D-E) has been variously de- 

 scribed as obpyriform. pyriform, clavate, oval and somewhat flattened, 

 oblong, spherical, or ovoid. One conspicuous or several small refractive 

 globules or granules may be present in the body. At the anterior end 

 of the spore a flagellum of varying length is attached. 



3. The unequally biflagellate "heterokont" zoospore is typical of the 

 Plasmodiophorales (Fig. 1 G, the left five spores in lowermost line) and 

 is said to have a spherical or an oval body. In some instances the flagella 

 are described as apically attached and oppositely disposed with the 

 shorter one anteriorly directed; in others they are simply termed "an- 

 terior" (short) and "posterior" (long). Both flagella terminate in a 

 whiplash (Fig. 2 L, p. 12). 



The peculiar situation, noted below, that prevails in the order Sapro- 

 legniales, in which both the remaining types of spores or their homo- 



Explanation of Figure I 



A-D. Posteriorly uniflagellate: A-B, Chytridiales; B-C, Blastocladiales; 

 C-D, Monoblepharidales. D-E. Anteriorly uniflagellate: Hyphochytriales. 

 E-F. Anteriorly biflagellate primary zoospores: Saprolegniales. F-G. Later- 

 ally biflagellate zoospores: Saprolegniales, Leptomitales, Lagenidiales, and 

 Plasmodiophorales. 



(From various authors, freehand. Read from left to right; letters limit the 

 various types). 



