88 THE LOWER FUNGI— PHYCOMYCETES 



The genus Micromycopsis Scherffel (1926: 167) based on M. 

 cristata Scherffel in Hyalotheca and M. fischerii Scherffel in 

 Zygogonium should be considered in this connection. 



Rhizidiaceae 



Although this family contains a larger number of genera than 

 any other in the order it is probably the least well known. The 

 forms are chiefly transient in character, and are with difficulty 

 kept under observation long enough for the completion of 

 satisfactory studies. The members of the group vary greatly 

 in morphology, and present many interesting features whose 

 further elucidation will tend to shed light on the general problem 

 of phylogeny in the order (see key, p. 48). 



In the following key the essential characters of the genera 

 are indicated, and to avoid unnecessary repetition these are 

 omitted in the text. For a more detailed taxonomic treatment 

 the student should consult von Minden (1911) or Fischer (1892). 

 It is highly probable that many as yet undescribed species exist 

 in nature. 



Key to Genera of Rhizidiaceae 



I. Mycelium wliolly intramatrical. 

 A. Sporangia epibiotic. 



1. Mycelium consisting of delicate, more or less branching 

 threads. 

 a. Resting spores when present epibiotic. 



(1) Mycelium usually monophagus; resting spore 

 germinating by svvarmspores. 

 (o) Sporangium lacking a subsporangial vesicle. 



1. Rhizophidium, p. 91 



(6) Sporangium provided with a subsporangial 

 vesicle. 



1'. Sporangium with an extramatrical 

 stalk. 



a'. Sporangium with a solid apical 

 spine; the stalk in open con- 

 nection with the sporangium; 

 saprophytes. 



2. Obelidium, p. 92 



h'. Sporangium lacking the apical 

 spine, separated by a septum 

 from the stalk; parasites. 



3. Podochytrium, p. 92 



