INTRODUCTION 41 



Zoospores cleaved out either within the sporangium or partly 



or wholly formed outside the sporangium, where they are 



usually surrounded by a more or less evanescent vesicle; 



motile spore always x of the secondary type 



Primarily aquatic; the thallus holocarpic, endobiotic, 



either unicellular or consisting at maturity of a series of 



unbranched or rarely branched segments of slight 



extent ; zoosporangia persistent Lagenidiales, p. 904 



Primarily terrestrial; thallus eucarpic, mycelial, and usually 

 both intra- and extramatrical; zoosporangia persistent 

 or deciduous (conidia) Peronosporales, p. 1012 



Forming conidia which are forcibly shot off from the tip of a conidio- 



phore Entomophthorales, p. 1061 



1 Scherffel (1925a) has reported primary flagellated zoospores in Olpidiopsis 

 oedogoniarum. 



