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

Key to the Species of Didymium

1. Lime-crystals merely whitening the peridial wall.
	A. Fructification plasmodiocarpous.
		a. White.
			O Capillitium with adherent vesicles			1. D. complanatum
			OO Capillitium simple			2. D. anellus
			OOO Capillitium much combined; spores 10–13 µ			3. D. wilczekii
			OOOO Capillitium crystal-bearing			18a. D. anomalum
		b. Yellow or tawny				4. D. fulvum
	B. Fructification normally of distinct sporangia.
		a. Sporangia sessile or nearly so; outer calcareous wall conspicuously developed				5. D. crustaceum
		b. Sporangia plainly stipitate.
			i. Peridium much depressed; umbilicate below.
				O Stipe white		6. D. squamulosum
				OO Stipe black.
					+ Larger, about 7.5–1 mm.	7. D. melanospermum
					++ Small, about .5 mm.	8. D. minus
					+++ Sporangia discoid	9. D. clavus
			ii. Peridium small, globose.
				O Stipe dark brown or black; columella dark, obsolete or none.		10. D. nigripes
				OO Stipe generally paler, of various tints of brown, orange, etc.
					+Columella pale or white, nearly smooth	11. D. xanthopus
					++ Columella, yellow, discoid, rough	12. D. eximium
			iii. Peridium turbinate, columella hemispheric			13. D. trochus
			iv. Peridium annulate			14. D. annulatum
2. Calcareous crystals forming a distinct crust.
	A. Fructification wholly plasmodiocarpous					15. D. dubium
	B. Sporangia ill-defined, sessile, plasmodiocarpous.
		a. Spores generally nearly smooth				16. D. difforme
		b. Spores very rough, obscurely banded				17. D. quitense
EXTRA-LIMITAL
		a. Sporangia discoid, spores reticulate				18. D. intermedium
		b. Stipe, columella, peridium, orange-brown				19. D. leoninum

1. Didymium complanatum (Batsch) Rost.

[Plate XVI]., Fig. 8.

• 1786. Lycoperdon complanatum Batsch, Elench. Fung., I., p. 251.
• 1829. Didymium serpula Fr., Syst. Myc., III., p. 126, Rost., App., p. 21.
• 1875. Didymium complanatum (Batsch), Rost., Mon., p. 151.
• 1899. Didymium complanatum (Batsch) R., Macbr., N. A. S., p. 85.
• 1911. Didymium complanatum Rost., List., Mycetozoa, 2nd ed., p. 127.

Fructification plasmodiocarpous, creeping, flattened, vein-like, annulate or reticulate, the dark-colored peridium covered with white, but not numerous crystals; hypothallus none; columella none; capillitium much branched, violaceous threads combined to form a rather dense net which bears numerous, peculiar, rounded vesicles, yellowish in color, 30–50 µ in diameter; spores minutely warted, 7–9 µ, violaceous-brown.

The defining characteristics here are the curious supplementary vesicles. These are evidently plasmodic, embraced, shot-through, by all the neighboring capillitial threads, withal warted like a spore. They remind of the curious, belated, spore-like but giant cells found in stipes, as in arcyriaceous forms. With all the wealth of his prolix, poetic, metaphoric tongue, the Polish author gives them abundant consideration. In the Mon., Tab. IX., Figs. 166 and 180, he clearly shows the structure, although in the explanation of the plate he has strangely mixed this species with D. crustaceum Fr. Under D. serpula Fries may refer to the present species, although there is nothing in his description to determine the fact. The same thing may be said of the description and figures of Batsch. Rostafinski, in the Monograph, seems to have been satisfied as to the identity of Batsch's materials: in the Appendix, he writes D. serpula, but gives no reason.

Rare. New York. England, France, Germany.

2. Didymium anellus Morgan.

[Plate XVIII.], Fig. 7.