54 THE LOWER FUNGI— PHYCOMYCETES 



sitism the group differs strikingly from the Myxogastres and 

 corresponds with the Woroninaceae and Synchytriaceae of the 

 Chytridiales. In the small and apparently rather definite 

 number (1-8) of zoospores freed in the germination of the 

 sporangium ("spore") the Plasmodiophoraceae resemble the 

 Myxogastres more than they do the Woroninaceae and Synchy- 

 triaceae where the number is usually much larger. Ignorance 

 of the facts concerning the position of nuclear fusion and reduc- 

 tion division in the cycle of the various groups, and conflicting 

 evidence concerning the presence or absence of a soral membrane 

 render these characters of little value for purposes of contrast. 



In summarizing the available facts it would seem that the 

 Plasmodiophoraceae resemble the Myxogastres less than they do 

 the Woroninaceae and Synchytriaceae. Their failure to form 

 a true Plasmodium is regarded in this connection as an essential 

 feature. However, in placing the family in the Chytridiales, 

 it should not be assumed that the relationship to members of 

 this order is necessarily close. It has been pointed out above 

 in the ordinal diagnosis that the Chytridiales constitute a large 

 assemblage of forms which seem to have been derived along a 

 number of different lines. A correctly drawn phylogenetic 

 tree would probably completely disrupt the group. These 

 forms have been treated together in one order merely because 

 they constitute the most primitive fungi, not because they 

 are regarded as a coherent group of closely related genera. A 

 more natural arrangement is much to be desired, but cannot as yet 

 be attempted. This situation makes much easier the inclusion 

 of the Plasmodiophoraceae in the group, and taking into con- 

 sideration the striking difference in the morphology of the swarm- 

 spore in the three families it does not seem unreasonable to 

 assume that the Woroninaceae and Synchytriaceae are as closely 

 related to the Plasmodiophoraceae as to each other. To the 

 writer it seems likely that these several groups have arisen more 

 or less in parallel from yet more primitive Protozoa, and wholly 

 independent of the Myxogastres which have arisen from the 

 same or different Protozoa along another Une. The existence 

 in a limited section of the Protozoa of a type of nuclear division 

 resembling the cruciform division of the Plasmodiophoraceae 

 indicates perhaps the origin of this family, but does not of neces- 

 sity preclude the possibility that other families, which now possess 

 a higher type of mitosis, have arisen from the same or a closely 



