usually compacted into a smooth continuous crust.
4. LEPIDODERMA. Wall of the sporangium with an outer layer of large
scales, consisting of bicarbonate of lime.
I. DIDYMIUM, Schrad. Sporangium simple, subglobose and stipitate, the
base commonly umbilicate, or sometimes sessile and plasmodiocarp; the
wall a thin membrane with an outer layer of minute stellate crystals of
lime. Stipe present or sometimes wanting; the columella mostly
conspicuous, sometimes thin or obsolete. Capillitium of very slender
threads, straight or often sinuous, stretching from the columella to the
wall of the sporangium, simple or outwardly sparingly branched at a
sharp angle. Spores globose, violaceous.
Didymium, together with Spumaria, is to be distinguished from all other
genera of the Myxomycetes by the covering of stellate crystals, like
hoar-frost, upon the outer surface of the sporangium.
Sec.1. CIONIUM. Columella prominent, subcentral, globose, obovoid, or
turbinate; the threads of the capillitium radiating in all directions to
the wall of the sporangium.
_A. Sporangium stipitate._
1. DIDYMIUM SQUAMULOSUM, A. & S. Sporangium variable in form and size,
small and globose, or large and much depressed, the base usually
umbilicate, stipitate, or sometimes sessile, and even plasmodiocarp; the
wall very thin and pellucid, with a thin, gray-white layer of stellate
crystals of lime, breaking up into subpersistent scales. Stipe short,
erect, snow-white, longitudinally furrowed or plicate; the columella
central, snow-white, various in shape, globose, obovoid, turbinate, and
stipitate or sessile. Capillitium of numerous colorless threads,
radiating from the columella and separating outwardly into several
branches. Spores globose, very minutely warted, dark violaceous, 8-10
mic. in diameter.
Growing on old wood, leaves, herbaceous stems, etc. Sporangium .4-.6-.8
mm. in diameter, the stipe scarcely longer than the diameter, often much
shorter or nearly wanting.
2. DIDYMIUM PROXIMUM, B. & C. Sporangium globose or depressed-globose,
the base more or less umbilicate, stipitate; the wall very thin and
pellucid, with a loose white covering of stellate crystals of lime, the
upper part breaking up and falling away. Stipe long, erect, tapering
upward, yellow-brown to reddish-brown, expanding at the base into a
small hypothallus; the columella central, white, turbinate, or discoid
turbinate. Capillitium of slender, colorless threads, radiating from the
columella, branching and often anastomosing. Spores globose, even, pale
violaceous, 8-10 mic. in diameter. Plate XII, Fig. 37.
Growing on old leaves, sticks, culms, etc. Sporangium .4-.6 mm. in
diameter, the stipe two or three times the diameter.
3. DIDYMIUM EXIMIUM, Peck. Sporangium depressed-globose, the base
umbilicate, sometimes very much depressed and also umbilicate above,
stipitate; the wall pale ocher or pale yellow, with a thin layer of
minute white crystals of lime, the upper part gradually breaking away.
Stipe long, erect, tapering upward, pale yellow-brown, darker below,
expanding into a small brown hypothallus; the columella central, large,
discoid, or sometimes rough and irregular, pale ochre or yellowish.
Capillitium of much-branched colorless threads, radiating upward and
downward from the columella. Spores globose, very minutely warted, dark
violaceous, 9-11 mic. in diameter. Plate XII, Fig. 38.
Growing on old leaves, sticks, etc. Sporangium .5-.6 mm. in diameter,
the stipe about twice the diameter.
4. DIDYMIUM MICROCARPUM, Fr. Sporangium small, globose, the base
slightly umbilicate, stipitate; the wall a dark-colored membrane,
covered with abundant snow-white crystals of lime. Stipe long, slender,
erect, delicately striate, yellow-brown to blackish in color, expanded
at the base into a small hypothallus; the columella small, globose,
sessile or substipitate, pale yellow-brown. Capillitium of pale brown
threads, somewhat branched and forming a loose net. Spores globose, very
minutely warted, violaceous, 6-7 mic. in diameter.
Growing on old wood, leaves, mosses, etc. Sporangium .4-.5 mm. in
diameter, the stipe two or three times as long. The species is more
particularly distinguished by its small spores.
5. DIDYMIUM MINUS, Lister. Sporangium depressed-globose, the base
umbilicate, stipitate, rarely sessile and plasmodiocarp; the wall a
dark-colored membrane with a thin layer of stellate crystals of lime,
breaking up gradually and falling away. Stipe erect or sometimes bent at
the apex, variable in length, rarely wanting, from pale brown to
blackish in color, rising from a small hypothallus; the columella
reaching the center, brown or blackish, rough, convex, subglobose or
pulvinate, substipitate. Capillitium of slender colorless threads,
radiating from the columella and more or less branched outwardly. Spores
globose, very minutely warted, violaceous, 8-10 mic. in diameter. Plate
XII, Fig. 39.
Growing in vast abundance in Spring on old leaves, bark, wood, etc.
Sporangium .4-.6 mm. in diameter, the stipe scarcely longer but usually
shorter than the diameter of the sporangium rarely absent. It is
considered by Lister to be a variety of _D. farinaceum_; it differs from
this species in its smaller and less-depressed sporangium and in its
smaller nearly smooth spores.
_B. Sporangia sessile._
6. DIDYMIUM EFFUSUM, Link. Sporangia gregarious or scattered, sessile on
a flattened base, convex above, various in shape, subrotund or by
confluence effused and venosely creeping; the wall very thin and
pellucid, invested with a thin flocculose layer of minute crystals of
lime. The columella hemispheric, rugulose, usually snow-white.
Capillitium of very slender colorless threads, furnished with numerous
minute protuberances, much branched and combined into a dense net.
Spores globose, very minutely warted, dark violaceous, 10-11 mic. in
diameter.
Growing on old leaves, wood, etc. Sporangium about .5 mm. in diameter or
thickness, sometimes confluent and more or less elongated as a
plasmodiocarp. This species is reported from the United States, but I
have seen no specimens.
7. DIDYMIUM PHYSAROIDES, Pers. Sporangia roundish or hemispheric, more
or less irregular and deformed, sessile or with a very short stipe, and
closely crowded together upon a strongly-developed common hypothallus;
the wall a dark colored membrane, with a thin layer of stellate crystals
of lime. The columella large and thick, divided into cells which are
filled with irregular lumps of lime, common to all the sporangia.
Capillitium of stout threads, usually simple, only rarely branched,
furnished with numerous fusiform swellings. Spores globose, minutely
warted, dark violaceous, 12-14 mic. in diameter.
Growing on old wood, bark, moss, etc. Reported from Carolina by Curtis.
It is said superficially to resemble somewhat _Physarum didermoides_.
Sec.2. PLACENTIA. Columella basal, much depressed, very thin or quite
obsolete, connate with the base of the sporangium; the threads of the
capillitium ascending to the wall of the sporangium.
_A. Sporangium stipitate._
8. DIDYMIUM FARINACEUM, Schrad. Sporangium hemispherical, more or less
depressed, the base profoundly umbilicate; the wall firm, rugulose,
dark-colored and nearly opaque, with a mealy coat of stellate crystals
of lime, rupturing irregularly. Stipe variable in length, rigid, erect,
black or sometimes rusty-brown, arising from a small hypothallus; the
columella broad, hemispherical or pulvinate, black, the lower side
connate with the wall of the sporangium. Capillitium of dark-colored
sinuous threads, simple or scarcely branched. Spores globose, dark
violaceous, minutely warted, 10-13 mic. in diameter. Plate XII, Fig. 40.
Growing on old wood, leaves, mosses, etc. Sporangium .6-.9 mm. in
diameter, the stipe about as long as the diameter of the sporangium or
sometimes much longer, usually, however, much shorter than the diameter
and almost concealed within the umbilicus. My specimens are from
Pennsylvania and Alabama. It is readily distinguished from _Didymium
minus_ by the much larger and more distinctly warted spores.
9. DIDYMIUM CLAVUS, A. & S. Sporangium pileate, very much depressed,
convex above and concave below, stipitate; the wall a dark-colored
membrane, thickly covered with minute white crystals of lime, except the
brown concavity underneath, the upper part breaking away, the lower
persistent. Stipe short, erect, rugulose, brown or blackish, expanding
at the base into a small hypothallus; the columella reduced to a thin
layer of minute brown scales upon the base of the sporangium.
Capillitium of simple or sparingly-branched threads, colorless at the
extremities and dark-colored between. Spores globose, even, violaceous,
6-8 mic. in diameter.
Growing on old leaves, sticks, herbaceous stems, etc. The sporangium
.6-.8 mm. in diameter, the stipe about the same length. Fries considered
this to be a mere variety of _D. farinaceum_, but it is readily
distinguished by its very small spores.
_B. Sporangia sessile._
10. DIDYMIUM SERPULA, Fr. Plasmodium yellow. Plasmodiocarp much
depressed, subrotund or usually more or less elongated, bent, flexuous
and reticulate; the wall dark-colored, with a thin layer of stellate
crystals of lime. Columella entirely wanting. Capillitium of very
slender threads, extending from base to upper surface, much branched,
the branches combined into a dense network; to these threads adhere
numerous roundish vesicles, composed of a brownish membrane, inclosing a
yellow coloring matter, the vesicles 30-50 mic. in diameter. Spores
globose, very minutely warted, violaceous, 7-8 mic. in diameter.
Growing on old leaves, bark, etc. The plasmodiocarp .6-.8 mm. in
thickness and extending from one to several millimeters in length. This
species is reported from the United States by Massee. It ought to be
readily recognized by its yellow plasmodium and the peculiar vesicles
adherent to the capillitium.
11. DIDYMIUM ANELLUS, Morgan, n. sp. Plasmodiocarp in small rings or
links, then confluent and elongated, irregularly connected together,
bent and flexuous, resting on a thin venulose hypothallus; the wall
firm, dark-colored, with a thin layer of stellate crystals of lime,
irregularly ruptured. Columella merely a thin layer of brown scales.
Capillitium of slender dark-colored threads, which extend from base to
wall, more or less branched, and combined into a loose net. Spores
globose, very minutely warted, violaceous, 8-9 mic. in diameter. Plate
XII, Fig. 41.
Growing on old leaves in woods in Spring. Plasmodiocarp in rings .3-.5
mm. in diameter, or often more or less elongated into links and chains,
which are bent and flexed in quite an irregular manner, the thread or
vein composing them about .2 mm. in thickness. A more minute species
than _Didymium serpula_, without characteristic thickenings upon the
threads of the capillitium, and wanting the peculiar large cells of this
species.
II. SPUMARIA, Pers. AEthalium composed of numerous elongated,
irregularly-branched sporangia, more or less closely compacted together
and confluent, seated upon a well-developed common hypothallus; the
walls of the sporangia a thin membrane with an outer layer of minute,
stellate crystals of lime. Each sporangium traversed by a central
subcylindric hollow columella, which extends also to the branches, but
does not reach to their apices. Capillitium of slender threads, more or
less branched, and combined into a network. Spores globose, violaceous.
Spumaria is essentially related to Didymium by the crystals of lime upon
the walls of the sporangia. Rostafinski's figure 158 can only be
regarded as ideal or diagrammatic. I am disposed to question the
existence of the central columella altogether; if it does exist, it must
be extremely defective.
1. SPUMARIA ALBA, Bull. Plasmodium white, amplectant. AEthalium variable
in form and size, resting upon a white, membranaceous hypothallus, and
usually covered by a white, friable, common cortex composed of minute
crystals of lime. The component sporangia elongated, irregular, more or
less branched, the branches rude, deformed, compressed, laterally
confluent, obtuse or pointed at the apex; the walls of the sporangia
thin and delicate, rugulose, pellucid, with a tinge of violet,
iridescent when divested of the crystals of lime. Capillitium of slender
threads, more or less branched and combined into a net; the threads dark
colored, with pellucid extremities, and furnished with occasional rings
or roundish swellings throughout their length. Spores globose, densely
spinulose, dark violaceous, 10-14 mic. in diameter. Plate XII, Fig. 43.
Climbing up and surrounding the stems of small shrubs, herbaceous
plants, culms of grasses, etc., especially those of living plants,
rarely effused upon old wood, bark, leaves, etc. The aethalium from two
or three to several centimeters in length, and with a radial thickness
of two or three to several millimeters. The following forms or varieties
have been distinguished as species at different times:
Var. 1. DIDYMIUM. Sporangia irregular, simple or lobed and branched,
lifted up on narrow, flat extensions of the hypothallus, as if furnished
with short white stipes; the common cortex wanting. This is _Didymium
spumarioides_, Fr.; it is probably a dwarf form of the next variety.
Plate XII, Fig. 42.
Var. 2. CORNUTA. AEthalium large and rugged in outline, cinerous from the
scanty cortex; the sporangia loosely compacted, the branches running
out into numerous free-pointed extremities. Capillitium of rather thick
threads, forming a dense net, with broad expansions at the angles.
Spores 11-14 mic. in diameter. This is _Spumaria cornuta_, Schum. It is
evidently the form so elaborately figured by Rostafinski, and which
Fries says abounds in Northern Europe.
Var. 3. MUCILAGO. AEthalium large, even and uniform in outline, covered
by a thick, white, common cortex; the sporangia laterally confluent and
densely compacted together throughout. Capillitium of rather slender
threads, forming a loose net, scarcely expanded at the angles. Spores
10-13 mic. in diameter. This is _Spumaria mucilago_, Nees, as figured by
Greville in the Scottish Cryptogamic Flora. The capillitium is figured
by McBride in The Myxomycetes of Iowa. This is the only form I have met
with in this country.
III. DIDERMA, Pers. Sporangia subglobose and stipitate or more often
sessile, sometimes plasmodiocarp; the wall a thin membrane, with an
outer layer composed of minute roundish granules of lime, which are
usually compacted into a smooth continuous crust. Stipe present or
mostly absent; the columella usually well developed. Capillitium of very
slender threads, stretching from the columella to the wall of the
sporangium, more or less branched, and combined into a loose net by
short lateral branchlets. Spores globose, violaceous.
This genus is easily recognized by the smooth crustaceous layer of lime
on the outer surface of the sporangium; in many cases this easily shells
off or breaks away. Such a coating occurs in a few species of Physarum,
but here the vesicles of lime attached to the threads distinguish them.
This is Chondrioderma of Rostafinski's monograph; the reason for coining
a new name and entirely discarding the old one is not apparent.
Sec.1. LEANGIUM. Sporangium usually stipitate; the wall at maturity
separating from the inner mass of spores and capillitium and splitting
in a stellate manner, the segments becoming reflexed.
1. DIDERMA RADIATUM, Linn. Sporangium depressed-globose, the base
flattened or umbilicate, stipitate or nearly sessile; the wall smooth,
whitish or pale brown, splitting from the apex downward into a few
reflexed irregular segments. Stipe short, thick, erect, tapering
downward, standing on a thin membranaceous hypothallus; the columella
large, convex, globose or obovoid, roughened. Capillitium of slender
dark-colored threads, radiating from the columella, simple or branching
outwardly. Spores globose, minutely warted, dark violaceous, 8-10 mic.
in diameter.
Growing on old bark and wood. Sporangium .8-1.2 mm. in diameter, the
stipe shorter than the diameter, sometimes nearly obsolete. Apparently
rare in this country.
2. DIDERMA FLORIFORME, Bull. Sporangium globose or obovoid, stipitate,
growing closely crowded together on a thin brown membranaceous
hypothallus; the wall smooth, varying in color from whitish or yellowish
to bright brown, splitting into irregular segments, which become
reflexed and revolute. Stipe long, erect, white or yellowish to brown;
the columella elongated, obovoid to clavate, roughened, colored as the
stipe. Capillitium of dark-colored threads, radiating from the columella
and sparingly branched. Spores globose, with minute scattered warts,
dark violaceous, 9-11 mic. in diameter. Plate XII, Fig. 44.
Growing on old wood of oak, hickory, etc., late in Autumn. Sporangium
.7-1.0 mm. in diameter before dehiscence, the stipe usually longer than
the sporangium. The color of stipe, columella and sporangium varies from
white through yellowish to brown; the spores are quite peculiar by
reason of their prominent scattered warts. I do not think _Chondrioderma
Lyallii_, Massee, can be maintained as a separate species.
Sec.2. STROMNIDIUM. Sporangia growing closely crowded together upon a thick
highly-developed calcareous common hypothallus, either seated upon it or
partially imbedded in its substance; the wall rupturing irregularly.
3. DIDERMA SPUMARIOIDES, Fr. Sporangia rather small, irregularly
subglobose, sessile, seated close together on a strongly-developed
whitish or yellowish common hypothallus; the wall white, rugulose,
covered by a dense farinaceous layer of lime. Columella convex,
roughened, white or yellowish, sometimes scarcely developed. Capillitium
rather scanty, of slender colorless threads, sparingly branched,
ascending from the columella. Spores globose, minutely warted,
violaceous, 8-10 mic. in diameter.
Growing on old leaves, bark, moss, etc. Sporangia .4-.6 mm. in diameter,
irregular and rugulose. On account of the pulverulent coat of lime on
the sporangium, Massee refers the species back to Didymium, where it was
placed by Fries.
4. DIDERMA STROMATEUM, Link. Sporangia large, subglobose, depressed,
irregular and angular from mutual pressure, closely crowded together on
a thick yellowish or pinkish common hypothallus; the wall smooth and
even, grayish-white or cinereous, with a thin closely connate outer
layer of minute granules of lime. Columella considerably elevated or
much depressed, convex, subglobose or quite irregular, white or colored,
as the hypothallus, especially at the base. Capillitium of abundant
colored threads, more or less branched and combined into a loose net.
Spores globose, minutely warted, violaceous, 8-10 mic. in diameter.
Growing on Hickory bark. The sporangia .5-.8 mm. in diameter, the
surface smooth. Rostafinski, in his Monograph, places this species as a
variety of _D. spumarioides_, but in the Appendix it is separated as a
species. The sporangia are quite different from those of _D.
spumarioides_, but I can see no difference in the spores.
5. DIDERMA GLOBOSUM, Pers. Sporangia subglobose, more or less irregular
from mutual pressure, closely crowded together on a thick, white
hypothallus, seated upon it or usually sunk into its substance at the
base; the wall with a white, smooth, and polished crustaceous outer
layer of lime, distinct and separable from the inner membrane, easily
breaking into fragments, and falling away: the inner membrane very thin,
rugulose, cinereous with granules of lime or free from them and
iridescent. Columella white, small, irregular, subglobose or
ellipsoidal, rarely wanting. Capillitium of slender, dark colored
threads, more or less branched and combined into a loose net. Spores
globose, very minutely warted, violaceous, 8-10 mic. in diameter.
Growing on old leaves. Sporangia .5-.8 mm. in diameter, the surface
smooth and polished.
6. DIDERMA CRUSTACEUM, Peck. Sporangia subglobose, irregular from mutual
pressure, closely crowded together on a thick, yellowish-white common
hypothallus, and at the base confluent with its substance; the wall with
a creamy white, smooth, crustaceous outer layer of lime, distinct and
separable from the inner membrane, and easily breaking up and falling
away; the inner membrane very thin, rugulose, cinereous and iridescent.
Columella whitish or cream colored, small, irregular, subglobose or
ellipsoidal, often wanting. Capillitium of slender, uneven, dark colored
threads, branched and combined into a loose net. Spores globose,
minutely warted, violet-black, opaque, 12-15 mic. in diameter. Plate
XII, Fig. 45.
Growing on old leaves, sticks, etc. A common species in this country.
Sporangia .7-1.0 mm. in diameter, the surface even but finely
pulverulent rather than polished. _Chondrioderma affine_, Rost., is said
to be the same species. It is readily distinguished from _D. globosum_,
by the much larger spores.
Sec.3. ASTROTIUM. Sporangia gregarious, scattered, or sometimes crowded and
confluent, often much depressed, sessile, rarely stipitate; the
hypothallus none or very scanty.
7. DIDERMA MICHELII, Lib. Sporangia orbicular, very much depressed,
often umbilicate above and concave underneath, stipitate or sessile,
gregarious, with the margins of the sporangia sometimes confluent. The
wall with a white crustaceous layer of lime, which soon ruptures around
the edges, allowing the upper part to break in pieces and fall away; the
inner membrane cinereous, rupturing irregularly. Stipe short, stout,
erect, arising from a small, circular hypothallus, whitish or
alutaceous, longitudinally rugulose, expanding at the apex, the wrinkles
running out as veins on the under side of the sporangium; the columella
much flattened, lenticular or discoid, alutaceous or pinkish.
Capillitium of very slender, colorless threads, simple or forking a time
or two, and connected by short branchlets at the extremities. Spores
globose, even, violaceous, 7-9 mic. in diameter.
Growing on sticks, leaves, herbaceous stems, etc. Sporangium .8-1.2 mm.
in diameter, the stipe shorter than the diameter, sometimes very short
or quite obsolete.
8. DIDERMA TESTACEUM, Schr. Sporangia circular or oval, much depressed,
sessile, without any hypothallus, gregarious, irregularly scattered,
sometimes close and even confluent. The outer calcareous layer of the
wall thick, smooth, crustaceous, separate and distinct from the inner
membrane, white or pinkish-white to rose-red in color, gradually
breaking up in pieces and falling away; the inner membrane thin,
pellucid, cinereous from the adherent granules of lime, irregularly
dehiscent from the apex downward. Columella hemispheric or depressed,
granulose-roughened, white, pinkish, or fleshy-red. Capillitium of very
slender, nearly colorless threads, more or less branched. Spores
globose, very minutely warted, 8-10 mic. in diameter.
Growing on old leaves, wood, mosses, etc. Very common in this country.
Sporangium .6-1.0 mm. in diameter, sometimes a little irregular,
especially the form growing on mosses, and occasionally confluent.