CHYTRIDIALES 45 



nized, to each of which may appropriately be applied the genus name 

 of the fungus which most nearly exemplifies it, that is, (1) Olpidi- 

 um type, (2) Entophlyctis type, (3) Chytridium type, and (4) Rhizidium 

 type. Other well-marked types may also be discerned, but they either 

 are regarded as variations or elaborations of those already named or 

 are so unique and occur in so few forms as to merit individual attention. 

 This arbitrary grouping is to be considered in no other light than that 

 of convenience. In the present state of our knowledge of the chytrids 

 it is impossible to make any sweeping statements concerning the deri- 

 vations and interrelationships of developmental types. It is apparent, 

 however, in taking the lower aquatic Phycomycetes as a whole, that 

 certain of these types occur not only in both the operculate and the 

 inoperculate chytrids but in other orders as well. Thus the Olpidium 

 type is found in the Chytridiales (Olpidium, Endochytrium oophilum), 

 the Anisolpidiaceae of the Hyphochytriales (Latrostium), the Sapro- 

 legniales (Ectrogella), and the Lagenidiales (Olpidiopsis, Sirolpidium, 

 Lagenidium oophilum, and so on). The failure to recognize the fact 

 that parallel body types have arisen independently in these different 

 groups has greatly confused and retarded significant studies on the 

 taxonomy and phylogeny of the lower aquatic Phycomycetes (Sparrow, 

 1933a, 1935b). 



In the first three of the developmental types about to be described 

 actual entry of the fungous protoplasm into the substratum (a process 

 first observed by Kloss, 1856a) is accomplished by means of a tenuous 

 tube produced by the encysted zoospore. This tube, perhaps aided by 

 enzyme action, penetrates the wall of the substratum and either con- 

 veys a part of the contents of the spore into the interior or retains the 

 contents, its tip then elongating and laying down the rudiments of the 

 vegetative system. In the fourth or Rhizidium type only the distal parts 

 of the rhizoids emanating from the encysted spore probably make 

 contact with and enter the substratum. 



1 . Olpidium type. — After the tip of the penetration tube in this type 

 has reached the lumen of the host cell the contents of the encysted zoo- 

 spore are conveyed to the inside (Fig. 3 A, p. 48). Here the naked mass 

 is surrounded by a pellicle, which soon becomes a discrete wall. With 



