Key 4:

SECTION 4:
Sporangium predominantly pyriform (the part of the sporangium proximal to the substrate is broadest), conical, or pyramidal.

Section 4

1. Organism saprophytic..........................................................................2
Organism parasitic..................................................................................3

2. Organism saprophytic on chitin........................................R. chitinophilum
Organism saprophytic on Cosmarium........................................R. ubiquetum

3. Organism parasitic on Blastocladia, Gonapodya, or Blyttiomyces...............4
Organism parasitic on other organisms....................................................12

4. Organism parasitic on Blastocladia or Gonapodya....................................5
Organism parasitic on Byttiomyces spinosus.......................R. blyttiomycerum

5. Organism parasitic on Blastocladia sp...................................................6
Organism parasitic on Gonapodya polymorpha.....................R. gonapodyanum

6. Resting spores present........................................................................7
Resting spores absent...........................................................................10

7. Resting spore wall spinous...................................................................8
Resting spore wall smooth.......................................................................9

8. Resting spore wall 2-layered........................................R. blastocladianum
Resting spore wall a single layer...............................................R. spinosum

9. Resting spore elliptical, 12 micrometers x 9micrometers.........R. urceolatum
Resting spore spherical, 5.5 micrometers diameter.......................R. lagenaria

10. Rhizoids present.............................................................................11
Rhizoids absent......................................................................R. stellatum

11. Rhizoids short and thin........................................................R. reflexum
Rhizoids thin, delicate, unbranched, arising from 2 axes.................R. rhizinum

12. Sporangium small, diameter and height ~ 5 micrometers......................13
Sporangium larger than 5 micrometers.....................................................15

13. Sporangial wall collapses after discharge...........................R. mischococci
Sporangial wall does not collapse after discharge......................................14

14. Sporangium sessile.............................................................R. minutum
Sporangia sessile and stalked..............................................R. androdioctes

15. Sporangium conical or pyramidal............................................R. conicum
Sporangium pyriform.............................................................................16

16. Sporangia abundant and numerous on host.........................................17
Sporangia usually single or few on host...................................................19

17. Endobiotic part a coralloid or poly-digitate haustorium.........R. coralloidium
Endobiotic part a richly branched rhizoid...................................................18

18. Sporangia with 1-3 discharge papillae, often terminating as short tubes.... .........................................................................................R. apiculatum
Sporangia with 1-3 discharge papillae, not terminating as short tubes.............
.................................................................................. .R. mycetophagum

19. Tip of discharge papilla attenuated....................................................20
Tip of discharge papilla not attenuated....................................................21

20. Parasitic on Apiocystis...........................................................R. braunii
Parasitic on Cryptomonas............................................................R. simplex

21. Rhizoid extensively branched............................................................22
Rhizoid tenuous, sparsely branched.........................................................25

22. Sporangium with one apical discharge papilla......................................23
Sporangium with one prominent apiculus and one sub-apical discharge papilla.. ..................................................................................R. pseudodistomum

23. Sporangia both pyriform and variable in shape .............................R. agile
Sporangia only pyriform.........................................................................24

24. Parasitic on Ophiocytium..........................................................R. sciadi
Parasitic on Tribonema........................................................R. zoophthorum

25. Sporangium usually tilted on surface of host...................R. granulosporum
Sporangium upright on surface of host.....................................................26

26. Sporangium subtended by an isodiametric stalk....................R. anomalum
Sporangium sessile...............................................................................27

27. Parasitic on Saprolegnia and Achlya..................................R. carpophilum
Parasitic on Chlamydomonas.....................................................R. acuforme
Parasitic on Eudorina...............................................................R. eudorinae


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