oo Columella yellow 20. _P. citrinum_ OO Sporangium not yellow. o Capillitial mass 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-mass 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-album_ _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_ xxx. Stipe snow-white, fragile 37. _P. leucopus_ xxxx. 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_