A._ Fructification aethalioid 1. _Fuligo_

_B._ Fructification plasmodiocarpous or of distinct
sporangia.

_a._ Peridium evidently calcareous.

i. Capillitium calcareous throughout 2. _Badhamia_

ii. Capillitium largely hyaline.

O Sporangia globose, etc.;
dehiscence irregular 3. _Physarum_

OO Sporangia vasiform or more or less
tubular

+ Dehiscence by a lid or more
or less circumscissile 4. _Craterium_

++ Dehiscence irregular,
peridium introverted 5. _Physarella_

_b._ Peridium apparently limeless, at least outside.

i. Plasmodiocarpous 6. _Cienkowskia_

ii. Sporangia distinct 7. _Leocarpus_

C. Extra-limital.

_a._ Sporangia stipitate, saucer-shaped, following
No. 3. _Trichamphora_

_b._ Sporangia elongate allantoid, etc., following
No. 1. _Erionema_

=1. Fuligo= (_Haller_) _Pers._

1753. _Mucor_ Linn., _Sp. Pl._ II., No. 1656 (?).
1768. _Fuligo_ Haller, _Hist. Helv._, Nos. 1233-1235, in part.
1801. _Fuligo_ Haller, _Pers. Syn._, p. 159.
1809. _Aethalium_ Link, _Diss._, I, p. 42.
1829. _Aethalium_ Fries, _Sym. Myc._, III., p. 92.

Sporangia undefined, obscurely woven in and out among each other forming
usually a cushion-shaped aethalioid mass. The outer layer sterile, often
calcareous, forming a fragile crust, more or less defined. The middle
layer sporiferous with calcigerous capillitium. The lowest layer a
membranous hypothallus.

The identity of this genus seems to have been recognized first by
Haller, _op. cit._, but by Persoon more closely defined and illustrated.
Link simply translated the name into Greek, for reasons less evident
now, and in this was followed by Fries. Haller's designation is now
probably securely fixed.

The sporigerous median structure of the fructifications, under whatever
specific name or names, is entirely confused. Sporangial walls, if ever
such there were, are hardly as such recoverable, seemingly _indicated_
only, in the changes to which the aethalium submits as in the ripening
the sporogenic plasm pa