Key 2:

SECTION 2:
Sporangium predominantly spherical at first, and urceolate after discharge.

Section 2

1. Saprophytic on pollen..........................................................................2
Parasitic on various hosts........................................................................3

2. Sporangia proliferate internally...............................R. novae-zeylandiensis
Internal proliferation of sporangia absent, zoospores released as upper part of sporangial wall splits, shrinks, or deliquesces...............................R. sibyllina

3. Sporangium with an apical collar and/or 4 prominent, plain teeth; parasitic on Coleochaete....................................................................R. brebissonii
Sporangium without an apical collar or prominent teeth...............................4

4. Sporangium small, 5-13 micrometers diameter........................................5
Sporangium larger, 15-50 micrometers diameter..........................................6

5. Sporangium 5-8 micrometers diameter; parasitic on Scenedesmus.............. .........................................................................................R. scenedesmi
Sporangium 3-13 micrometers diameter; parasitic on Gemellicystis................. .........................................................................................R. uniguttulum

6. Zoospores discharged and liberated successively, or forcibly as a loose mass....................................................................................................7
Zoospores discharged in a vesicle.............................................................8

7. Zoospores discharged and liberated successively; parasitic on oogonia of Vaucheria.............................................................................R. vaucheriae
Zoospores ejected forcibly as a loose mass; parasitic on wheat roots......................................................................................R. graminis

8. Rhizoid branched; parasitic on the resting spore of Ceratium hirundinella..... .................................................................................................R. nobile
Rhizoid unbranched.................................................................................9

9. Rhizoid broad, tubular; parasitic on Closterium.......................R. tubulatum
Rhizoid slender, thread-like; parasitic on Anguillula.....................R. vermicola



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