Key 5:
SECTION 5:
Sporangium predominantly obovoid, obovate, or obpyriform (the part of the sporangium distal to the substrate is broadest).
- Sporangium born on a stalk..............................................................2
Sporangium sessile on substrate.......................................................8
- Stalk robust....................................................................................3
Stalk thin.......................................................................................4
- Sporangium multi-pored....................................R. spinosum Willoughby
Sporangium single-pored........................R. spinosum Karling (homonym)
- Stalk isodiametic, short or long.........................................................5
Stalk clavate...............................................................R. pedicellatum
- Spores discharged through 1-4 pores..................................................6
Spores released as entire sporangial wall deliquesces............R. piriformis
- Apical pore opening broad, rim reflexed..............................R. echinatum
Apical pore(s) not broad, rim not reflexed...........................................7
- Rhizoids branched...............................................................R. fulgens
Rhizoids unbranched.....................................................R. obpyriformis
- Zoospore discharge through a pore....................................................9
Upper half of sporangium deliquesces to liberated..............................12
- Discharge pore apical.....................................................................10
Discharge pore lateral....................................................R. parasiticum
- Sporangium conchiforme in shape...................................R. conchiforme
Sporangium clavate, pear-shaped, or oval..........................................11
- Sporangium clavate, rhizoids robust and branched.................R. clavatum
Sporangium pear-shaped or oval, rhizoid very slender...............R. ovatum
- Rhizoid unbranched............................................................R. clinopus
Rhizoid branched, coarse, tapering.....................................R. pelagicum