The North American Slime-Moulds / A Descriptive List of All Species of Myxomycetes Hitherto Reported from the Continent of North America, with Notes on Some Extra-Limital Species

by Thomas H. Macbride

Rostafinski approved the good intention of Fries, but in the Monograph, he entirely re-cast the genus as constituted by Fries; actually called the species 'first cited' a typical physarum! Would not have it in the new genus at all, first or last; but instead took the second species of Fries as the type and added several forms, some from the Friesian list, to make up a respectable group.

Until quite recently writers on the subject have generally approved the course adopted by the Polish author. The arrangement showed features of convenience, even if artificial to a degree. Perhaps we gain advantage in all directions if we treat the original genus Physarum as a whole, but in the key take advantage of Fries' suggestion. We may write—

Key to the Species of Physarum

1. Capillitium irregularly reticulate throughout; calcic nodes various	Physarum
2. Capillitium more regular, especially below, furcate; nodes fusoid	Tilmadoche

SECTION I. PHYSARUM

I. Fructification not stipitate, more or less plasmodiocarpous.
	1. Peridium simple.
		a. Calcareous deposits yellow						1. P. serpula
		b. Calcareous deposits reddish or orange						2. P. lateritium
		c. Calcareous deposits white, peridium rugulose						3. P. vernum
	2. Peridium double.
		a. Fructification flatly compressed						4. P. sinuosum
		b. Fructification less compressed, rounded.
			i. Outer peridium white					5. P. bitectum
			ii. Outer peridium brown or brown-tinged					6. P. bogoriense
			iii. Outer peridium yellow; capillitium yellow					7. P. alpinum
II. Fructification of sporangia more or less distinct.
	A. Sporangia sessile, globose, ovoid, reniform, etc.
		1. Peridium double.
			a. Sporangia white, peridium testaceous.					8. P. diderma
			b. Sporangia tinged with yellow.
				i. Sporangia as if interwoven, compressed				9. P. contextum
				ii. Sporangia more nearly free, distinct.
					o Spores pale, inner peridium brittle			10. P. conglomeratum
					oo Spores spinulose, dark violet			11. P. mortoni
			c. Sporangia brown, dehiscence revolute					12. P. brunneolum
		2. Peridium simple, calcareous, flaky.
			a. Sporangia grey, plasmodiocarpous; spores dusky, 10–12 forms of 3
			b. Sporangia grey, more or less dense; spores violet, 6–7					13. P. cinereum
			c. Calcareous deposits yellow or greenish, spores 7–9					14. P. virescens
			d. Sporangia rusty or reddish brown, more or less dense					15. P. rubiginosum
			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 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
					oooo Sporangia obovate, compound, clustered, 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
						xxx. Stipe red or reddish brown		44. P. citrinellum
						xxxx. Stipe yellowish, flaccid, sporangia leocarpine		45. P. albescens
						xxxxx. 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
					ooo Capillitium nodes pure yellow.
						x. Capillitial threads yellow		49. P. galbeum
						xx. Capillitial threads hyaline		50. P. tenerum
						xxx. Peridium iridescent.
							+ Capillitium persistent	51. P. flavicomum
							++ Capillitium less persistent, larger	52. P. bethelii

SECTION II. TILMADOCHE

I. Æthalioid, gyrose or irregular			53. P. gyrosum
II. Fructification stipitate.
	1. Sporangia irregular, often convolute, involved		54. P. polycephalum
	2. Sporangia simple, nutant, discoidal.
		a. Thin-walled, grey or white.	55. P. nutans
		b. Vari-colored, yellow, greenish, orange, etc.	56. P. viride

1. Physarum serpula Morgan.

[Plate IX]., Figs. 6, 6a, and 6b.