CHYTRIDIACEAE 9 



each order containing at least one fungous family ; propagation by fission and zoogo- 

 nids ; sexual reproduction present in most. 



Order 3. PROTOCOCCALES 



Typically one-celled algae, usually dividing by fission and producing zoogonids ; 

 sexual reproduction often lacking; one fungous family. 



Family 7. CHYTRIDIACEAE 



/ : 286, SCHROETER 65 



Mycelium lacking or in the form of delicate protoplasmic threads, rarely of 

 hyphae, one-celled ; sporangiophore lacking or but slightly developed ; sporangia 

 producing zoogonids, thin-walled and ripening quickly, or thick-walled and resting 

 for a time (resting sporangia); sexual reproduction present in a few forms, the 

 sex organs scarcely distinguishable. 



Key to the Subfamilies 



I. Resting sporangium asexual, rarely formed by the union of two zoogonids 



1. Mycelium completely lacking 



a. Sporangia separate, one formed from each fruit-mass 



Olpidiae 



b. Sporangia in sori, formed by division of fruit-mass 



Synchytriae 



2. Mycelium present 



a. Mycelium of delicate transient strands 



( 1 ) Mycelium limited to one terminal sporangium 



Rhizidiae 

 (2) Mycelium extended, sporangia intercalary and terminal 



Cladochytriae 



b. Mycelium consisting of permanent hyphae 



Hyphochytriae 



II. Sexual resting spores formed by union of two sporangia and passing of con- 



tents of one into the other Oochytriae 



III. Sexual spores formed by conjugation Zygochytriae 



Subfamily Olpidiae 



SCHROETER 6j 



Mycelium lacking; fruit-mass endobiotic, globose, elliptic, rarely subclavate. 

 undivided, finally forming a simple zoosporangium or resting sporangium, in wlvch 

 zoospores are formed after a period of rest. 



I. Fruit-body amoeboid before maturity Reessia 7:304, S. 67 



II. Fruit-body without movement 



1. Sporangia free in the host-cell 



a. Membrane delicate, dissolving to free zoospores 



Sphaerita 7:314, S. 67 



b. Membrane firm, with a definite opening 

 (1) Sporangia globose or elliptic 



(a) Sporangia with 1, rarely 2, openings 



