The North American Slime-Moulds Part 33

New York, Pennsylvania, Ohio, Iowa, Nebraska. Probably to be found throughout the eastern United States.

2. DIDERMA SPUMARIOIDES _Fries_.

1829. _Diderma spumarioides_ Fries, _Syst. Myc._, III., p. 104.

1833. _Physarum stromateum_ Link., _Handb._, III., p. 409.

1876. _Chondrioderma stromateum_ (Lk.) Rost., _App._, p. 18.

Sporangia sessile, crowded, spherical, or by mutual pressure irregular, white; the peridium plainly double, but the layers adhering, the outer more strongly calcareous, but very frail, almost farinaceous; hypothallus more or less plainly in evidence, white or pale alutaceous; columella distinct, though often small, globose, yellowish; capillitium variable in quant.i.ty, sometimes abundant, brown, somewhat branching and anastomosing outwardly, the tips paler; spores minutely roughened, dark violaceous, about 10 .

This species has the outward seeming of a didymium, but is plainly different as that genus is here defined, since the calcareous crust, although inclined to be pulverulent, is made up of minute granules, not crystals, of lime. The hypothallus is sometimes hardly discoverable, anon well developed, out-spread, rugulose, far beyond the limits of the fructification. In his _Monograph_, p. 175, Rostafinski includes here _Physarum stromateum_ Link. In the Appendix he is inclined to raise Link's form to the dignity of a distinct species, basing the diagnosis upon the superposition of the sporangia in certain cases, a feature entirely unknown to Link's description and of extremely uncertain value, since by their crowding the sporangia are liable always to be pushed above each other. We therefore regard _C. stromateum_ (Link) Rost. as a synonym of the present species, as the description, Link, Handb., III., 409, indicates, so far as it goes.

3. DIDERMA SIMPLEX (_Schroet._) _Lister._

1885. _Chondrioderma simplex_ Schroet., _Krypt. Fl. Schles._, III., 1, p. 123.

1911. _Diderma simplex_ List., _Mycetozoa, 2nd ed._, p. 107.

"Plasmodium bright yellowish brown." Sporangia gregarious, sessile, globose or depressed globose, .3-.5 mm., or anon plasmodiocarpous, brown or brick-red when fresh, becoming paler, ochraceous, etc.; hypothallus everywhere in evidence; columella ill-defined; capillitium scanty, the threads delicate, pale, branching as they join the peridial wall; spores dull violaceous, slightly roughened, 8-10 .

A rather crude, primitive representative of this beautiful genus. The inner peridium seems to be lacking,--a comfort to Rostafinski! Rare. Our best specimens are from New Jersey, by courtesy of Dr. C. L. Shear.

These went to fruit on leaves and branches of _Vaccinium_. It seems to affect the heather of Europe, moorland, etc. I have also specimens from the herbarium of the lamented Dr. Rex. These are more plasmodiocarpous, but open beautifully by a median fissure as in _Physarum sinuosum_ Bull. In no American gathering that I have examined does the capillitium show calcareous thickenings as described by the British text.

4. DIDERMA GLOBOSUM _Persoon._

PLATE VII., Figs. 5, 5 _a_.

1794. _Diderma globosum_ Pers., _Rom. N. Mag. Bot._, I., p. 89.

1875. _Chondrioderma globosum_ (Pers.) Rost., _Mon._, p. 180.

Sporangia more or less closely gregarious, sessile, globose or by mutual pressure prismatic or polyhedral, white, the outer wall smooth, polished, crustaceous, fragile, far remote from the inner, which is thin, smooth, or rugulose, iridescent blue; hypothallus usually p.r.o.nounced and spreading beyond the sporangia, sometimes scanty or lacking, columella variable, sometimes very small, inconspicuous, sometimes large, globose, ellipsoidal, even pedicellate; capillitium abundant, brown or purplish brown, branching and occasionally anastomosing to form a loosely constructed superficial net; spores globose, delicately spinulose, 8 .

This species seems rare in this country. We have specimens from Iowa. It is distinguished by small spores and generally snow-white color.

Lister has thrown doubt upon Rostafinski's definition of this form--_Mycetozoa_, p. 78. Almost everything distributed in the United States under this name belongs in the next species. Reported also from Ohio,--_Morgan._ Washington. But:--it should be found in Europe, where first described!

There are two ways to meet the difficulty. In the first place it seems probable that a small-spored form really hides somewhere in Europe. The difference between the _Monograph_ measurement and the size admitted for _D. crustaceum_ Pk., evidently considered by Mr. Lister as type and so used in his ill.u.s.tration, Pl. 85, is too great to be esteemed merely an error. That added .3 (Rost.) indicates caution, the average of several measurements. Our _D. globosum_ may represent what the _Monograph_ describes.[32] In the second place we may as American students mistake larger and more globular forms of something else, of _D. spumarioides_ Fr., whose spores are but little larger; or of _D. effusum_ (Schw.) Morg., where the flattened plasmodiocarps anon splatter out to globose drops of polished whiteness, and whose spores are 8 . But even here the chances of error are small. In the species last named the columella or sporangial base is alutaceous, not white; in Fries' species, while the columella if present may be white, the peridial walls are different, difficult to distinguish.

For these reasons, _D. globosum_ Pers. may stand, waiting further light from Europe.

5. DIDERMA CRUSTACEUM _Peck._

PLATE VII., Fig. 7

1871. _Diderma crustaceum_ Peck, _Rep. N. Y. Mus._, XXVI., p. 74.

1889. _Chondrioderma crustaceum_ (Peck) Berl., _Sacc._, VII., p. 373.

Plasmodium at first watery, colorless, becoming at length milky white; sporangia closely crowded or superimposed, in a cushion-like colony, creamy white, globose, imbedded in the substance of the hypothallus, the outer peridium smooth, delicate, crustaceous, fragile, remote from the blue iridescent inner membrane; hypothallus prominent; columella variable, generally present, globose; capillitium dark-colored, the threads branching and combining to form a loose net; spore-ma.s.s black, spores by transmitted light dark violaceous, delicately roughened, 12-15 .

Common. Readily to be distinguished from the preceding by the larger spores and more crowded habit. New England west to Nebraska.

The didermas are generally delicately beautiful. The outer wall in the present species is like finest unglazed china, softly smooth, and yet not polished, often absolutely white, with porcellanous fracture. An inter-parietal s.p.a.ce separates the outer from the inner wall, so that the former may be broken, bit by bit, without in the least disturbing the underlying structure. The inner wall is ashen or gauzy iridescent green, sending back all colors in reflected light. The spores are violet, deeply so when fresh, the capillitium strong and likewise tinted; the columella pa.s.sing down and blending with the common snow-white hypothalline base. The distinct habits of the two species are represented in Figs. 5 and 7. In the one the distinct sporangia are a.s.sociated but not crowded; in the other all are ma.s.sed together in quite aethalioid fashion, forming circ.u.mambient, chalky ma.s.ses of considerable size, 2 or 3 cm., overcrowded, superimposed, where the sporangia are regular in shape and size by reason of mutual pressure.

The plasmodium develops in forests and orchards, among decaying leaves, but is inclined to rise as maturity draws near, to ascend some twig erect, or the stem of a living plant to the height of several inches where the sporangia at length appear "heaped and pent", an encircling sheath, conspicuous after the fashion of a spumaria for which it is indeed sometimes mistaken.

6. DIDERMA LYALLII (_Ma.s.see_) _Macbr._

PLATE XVIII., Figs. 5 and 5 _a_

1892. _Chondrioderma lyallii_ Ma.s.see, _Mon._, p. 201.

1894. _Chondrioderma lyallii_ Ma.s.s., List., _Mycetozoa_, p. 81.

1899. _Diderma lyallii_ Ma.s.s., Macbr., _N. A. S._, p. 99.

1911. _Diderma lyallii_ List., sub-species, _Mycetozoa, 2nd ed._, p. 105.

Sporangia obovate, more or less closely crowded, white, stipitate, about 1 mm. in diameter, the outer peridium firm, stout, encrusted, especially above, with granular ma.s.ses of lime, the inner well developed, more or less cartilaginous, opaque, yellow or buff-colored; hypothallus well developed, venulose, white, pa.s.sing up unchanged to form the short, stout stipe and lower outer peridium; columella prominent, half the height of the sporangium, brown; capillitium of short, brown threads, rigid, much branched, forming a net, widened irregularly and especially at the net-nodes; spore-ma.s.s black, spores by transmitted light bright brown, rough, 15-17 .

A very distinct species; large, fine, showy sporangia in more or less crowded cl.u.s.ters spring from a snow-white, common hypothallus. First reported from western Canada. Our first specimens were collected by the late Mr. Charles Irish, on the eastern slopes of the Sierras, in Nevada; now coming in abundantly from all the western mountains to the Pacific.

7. DIDERMA TESTACEUM (_Schrad._) _Pers._

PLATE VII., 4, 4 _a_, and 4 _b_.

1797. _Didymium testaceum_ Schrad., _Nov. Gen. Plant._, p. 25.

1801. _Diderma testaceum_ Persoon, _Syn._, p. 167.

1873. _Chondrioderma testaceum_ (Schrad.) Rost., _Vers._, p. 13.

1874. _Diderma mariae-wilsoni_ Clinton, _Rep. N. Y. Mus._, XXVI., p. 74.

1899. _Diderma testaceum_ (Schrad.) Pers., Macbr., _N. A. S._, p. 99.

1911. _Diderma testaceum_ Pers., List., _Mycetozoa, 2nd ed._, p. 106.

Sporangia gregarious, sessile, depressed-spherical or sometimes elongate, small, 1 mm. or less, rose-white, smooth, the outer peridium crustaceous, rather thick and persistent, polished, slightly raised above the inner, which is dull ashen and more or less wrinkled; hypothallus none; columella prominent, hemispherical in the typical rounded forms, slightly rough, reddish or reddish alutaceous; capillitium usually abundant, of slender, delicate pale or colorless threads, little branched, and smooth; spores violaceous-brown, minutely roughened, 8-9 .

A very beautiful species occurring at the same time as the preceding and in similar situations. All our specimens from the west are on dead leaves of oak; some eastern gatherings are on moss. Easily recognized when fresh by its delicate pink or roseate color; weathered specimens are white, and might be confused with forms of _D. reticulatum_, but the sporangia in the present species are less flattened and only rarely in special situations run off to linear or plasmodiocarpous shapes characteristic of _D. reticulatum_.

Not common, although widely distributed from east to west. New England, New York, New Jersey, South Carolina, Ohio, Illinois, Iowa, Nebraska, California (_Harkness_), Washington, Oregon.

8. DIDERMA NIVEUM (_Rostafinski_) _Macbr._

PLATE XVIII., Fig. 11 and 11 _a_

1875. _Chondrioderma niveum_ Rost, _Mon._, p. 170.

1877. _Diderma albescens_ Phillips, _Grev._, V., p. 114.

Sporangia gregarious, scattered, or more often crowded, sessile, depressed-spherical, sometimes ellipsoidal or elongate, white, the outer peridium crustaceous, chalky, smooth and fragile, the inner distinct, delicate, ochraceous; hypothallus scant or none; columella well developed, globose or hemispherical, orange-tinted or ochraceous; capillitium abundant, made of threads of two sorts, some purplish or dusky, with pale extremities, uneven, others more delicate and colorless, and with wart-like thickenings, all sparingly branched; spores violet-brown, minutely roughened, 9-10 .

This species is not common. From Colorado we have fine specimens typical in every way. Specimens from Washington are flat so far as at present at hand; probably represent _D. deplanatum_ (R.) List., which the last named author regards as varietal of the present species, entering it and _D. lyallii_ as sub-species 2 and 1 respectively. _D. deplanatum_ may perhaps be best so disposed of; but _D. lyallii_ is distinguished at sight, as well as by microscopic characters, spores nearly twice as great, rougher and different in color.