_e._ Sporangia minute, lignicolous, the fructification much extended upon a hypothallus, lime deposit tawny 16. _P. instratum_
_f._ Sporangia white, depressed, annulate, sometimes with short stipes 17. _P. megalosporum_
3. Peridium simple, not flaky, small .2-.3 mm., heaped 18. _P. confertum_
B. Sporangia, at least some of them, stipitate.
_a._ Sporangia columellate.
i. Columella small, usually conical.
O Sporangium yellow.
o Columella white 19. _P. melleum_
oo Columella yellow 20. _P. citrinum_
OO Sporangium not yellow.
o Capillitial ma.s.s persistent.
+ Sporangia globose, pallid or white 21. _P. globuliferum_
++ Sporangia blue or lilac, rose, etc. 22. _P. lilacinum_
+++ Sporangia drab or brownish 23. _P. murinum_
++++ Sporangia wine-red 24. _P. pulcherrimum_
oo Capillitial-ma.s.s less persistent; orange 25. _P. pulcherripes_
ii. Columella long, 4-5 the sporangium non-calcareous. 26. _P. penetrale_
iii. Columella large globose 27. _P. luteo-alb.u.m_
_b._ Sporangia without columella.
i. Sporangia nucleate, calcareous at center.
O Stipe yellow 28. _P. nucleatum_
OO Stipe white 29. _P. wingatense_
ii. Sporangia non-nucleate.
O Sporangia purple 30. _P. newtoni_
OO Sporangia blue, spotted with red 31. _P. psittacinum_
OOO Grey or white, iridescent betimes.
o Sporangia white, discoidal; stipe yellow 32. _P. discoidale_
oo Sporangia lightly calcareous, iridescent, sub-globose, diam. about = to the stout, brown, slightly wrinkled stipe 33. _P. leucophaeum_
ooo Sporangia globose or sub-globose.
x. Small, .5 mm.
+ Stipe erect, clear brown 34. _P. nodulosum_
++ Stipe weak, yellow, stuffed 35. _P. maculatum_
xx. Larger, lime-capped; stipe strand-like 36. _P. didermoides_
x.x.x. Stipe snow-white, fragile 37. _P. leucopus_
x.x.xx. Stipe generally distinctly fluted
+ Sporangia laterally compressed, fan-shaped 38. _P. compressum_
++ Sporangia typically globose, umbilicate below, connate, etc., strongly calcareous 39. _P. notabile_
+++ Sporangia reniform, concave below _P. affine_, see under 38
++++ Sporangia larger, to 1 mm., nearly limeless, iridescent 40. _P. tropicale_
oooo Sporangia obovate, compound, cl.u.s.tered, the stipe fuscous, fluted, short. 41. _P. nicaraguense_
OOOO Sporangia yellow, rarely iridescent or brown.
o Capillitial nodes white.
x. Stipe also white 42. _P. sulphureum_
xx. Stipe flesh-colored, spores smaller 43. _P. carneum_
x.x.x. Stipe red or reddish brown 44. _P. citrinellum_
x.x.xx. Stipe yellowish, flaccid, sporangia leocarpine 45. _P. albescens_
x.x.xxx. Stipe very short or none, sporangia cylindric, brown 46. _P. variabile_
oo Capillitium nodes yellow or orange-yellow.
x. Badhamioid, larger,--to .8 mm. 47. _P. auriscalpium_
xx. Physaroid, base persistent 48. _P. oblatum_