| 1. Form a. Plasmodium yellow; cortex yellow, or orange-brown, strongly calcareous friable; form indefinite | F. ovata |
| 2. Form b. Cortex less calcareous porose, yellowish brown, fructification definite, pulvinate | F. rufa |
| 3. Form c. Cortex smooth, persistent; fructification small, less than two inches | F. laevis |
| 4. Form d. Plasmodium yellow; cortex none; capillitium yellow, fructification thin, sometimes wide-spread | F. flava |
| 5. Form e. Plasmodium violaceous, dark; cortex almost none; whole mass reddish or violet | F. violacea |
1. Form a. Fuligo ovata (Schaeff.) Pers.
Plasmodium bright yellow; æthalium pale brown, or yellowish-ochraceous, of variable size and shape, one to many cm. in diameter, and one to two cm. thick, enclosed by a distinct calcareous crust, which varies in texture, thickness, and color; capillitium well developed but variable in color, form, and extent; spore-mass dull black, sooty; spores spherical, purplish brown, nearly smooth, 7–9 µ.
Under this name may be placed our most common form. Rising with an abundant yellowish creamy plasmodium from masses of decaying vegetation, lumber, sawdust, half buried logs, it creeps about with energy unsurpassed, coming to rest only in some position specially exposed, as the top of a log or stump, the face of a stone or post, or even the high clods of a cultivated field! The fructification is large, yellow, or at most pale ochraceous, the surface when mature extremely friable like dry foam. Bulliard figures this phase well on Plate 424, Fig. 2, and calls it Reticularia (Fuligo) hortensis, from its affecting the soils of gardens. More than thirty fructifications have appeared at one time, varying in size from one to twenty cm. in a field of potatoes, well tilled, and less than an acre in extent! Such is life's perennial exuberance on this time-worn old world of ours!
Schæffer's plate CXII represents probably the same thing. So also Bolton's plate, CXXXIV. Sowerby's Fig. 2 on plate 199, and figures 1 and 2 on Greville's plate 272 possibly also depict this form. Persoon calls this F. vaporaria because it frequents hotbeds and the like, and believes this to represent the "untuosus flavus" of Linnée, although he thinks Schæffer's specimens do not. The calcareous internal structure is white.
2. Form b, F. rufa Pers.
This type of Fuligo is very different from the preceding in form, habit, and color. In form it is much more definite, usually thick, well-rounded and with some solidity. The interior fructification is gray throughout, much less expanded than in a; in fact does not resemble a at all! The cortex is porose but firm, orange at first, but becoming tawny with age, even in the herbarium. Bulliard figures it well, plate 380, Fig. 1, and Sowerby's Fig. 1 on plate 399 is also good, as are also Greville's figure 3 on plate 272 showing the two colors referred to. Not uncommon in the forest from June till September, but far more rare than a: always well-marked, with no other forms associated.
3. Form c, F. laevis Pers.
[Plate X]., Fig. 2, 2 a, 2 b.
This is a still more specialized type of the group. The fructification is usually small, smooth, about an inch in diameter and sometimes nearly as thick; the cortex rusty brown, enduring, persisting often when all the sporiferous grayish mass has been distributed through chinks, or from below. The figure 2 on plate X. shows this form. This also is a forest species, is autumnal rather, but may be taken sometimes as early as July. The cortex is not at all porose or spongy, in color reddish or brown, fragile indeed, but not to the touch, in the herbarium enduring for years.