The North American Slime-Moulds Part 16

Plasmodium scarlet. Sporangia globose or cylindric, sessile or sometimes narrowed to a stem-like base as if short-stipitate, olivaceous brown with sometimes a flush of red; the peridium simple, thin rugulose or plain, the calcareous scales few, or apparently included; columella none; capillitium dense, the nodules rather large, angular, rusty brown; spores dull violaceous, gently roughened, about 10 .

A beautiful well-marked species, but evidently rare in North America.

Our only typical specimens are from the gatherings by Mr. Wingate, part of which is by Lister referred to this species, _Mycetozoa, 2nd ed._, p.

82.

_P. rubiginosum_ Fr. in the _N. A. S._, 1899, is based on certain west coast specimens now known as _Badhamia decipiens_ Berk.

In Colorado there occurs a plasmodiocarpous form of the species. It has the characteristic spore and capillitium but in form and habit differs very decidedly. The fructification is a delicate netted plasmodiocarp, the tubule about .5 mm., bright red; the peridium simple, cartilaginous, dehiscent from above, and flecked with just here and there a red calcareous scale.

Collected at Palmer Lake; _Professor Bethel._

16. PHYSARUM INSTRATUM _Macbr. n. s._

1899. _Physarum thejoteum_ Macbride, _N. A. S._, p. 36, not Fries, as cited.

1911. _Physarum virescens_ Ditmar, Lister, _Mycetozoa, 2nd ed._, p. 83.

Sporangia very small, closely crowded on a delicate, more or less visible hypothallus, often connate, but not superimposed, sub-spherical, dull orange, brownish or tawny; peridium thin, violaceous, covered with very minute yellow calcareous scales; columella none; capillitium lax, sometimes almost wanting; the nodules small, yellowish or brownish, occasionally confluent; spore-ma.s.s violaceous, spores by transmitted light, violet-tinted, smooth or nearly so, 6-7 .

Not uncommon in the Mississippi valley, where it sometimes is pa.s.sed by the collector as an immature form of some other species. The appearance is very characteristic, unlike _P. virescens_ in both habit, size, and color. Colonies are quite often three inches in length. The most common habitat seems to be rotten oak, especially fragments of charred logs, etc.

Ohio, Illinois, Missouri, Iowa, Nebraska.

This species presents a decidedly well-marked form, so much so that it may be easily recognized at sight, without a lens. It therefore requires special discussion, and although in the spore-characters and some minor but not determinative details it agrees with _P. virescens_ Ditm. to which it is by European authors sometimes referred, it seems nevertheless deserving of specific recognition, since in its entire habit and expression it is not only completely different but is constant in its specific peculiarities, much more so than is the suggested related form.

In the first edition of this work, the form was referred to _Physarum thejoteum_ of Fries. This was the judgment of our American colleague, Professor A. P. Morgan whose work in this group is widely recognized.

Fries admits, _Syst. Myc._, III., p. 142, that while he deems _P.

thejoteum_ very distinct, he yet has not seen _P. virescens_ Ditm.!

Since our form apparently does not occur in Europe, specimens which the distinguished author had before him were doubtless representatives of the now commonly recognized species of Ditmar.

For these reasons it seems appropriate to give the American type a suitably descriptive t.i.tle.

17. PHYSARUM MEGALOSPORUM _Macbr._

PLATE XVI., Figs. 7 and 7 _a_.

1917. _Physarum melanospermum_ Sturgis, _Mycologia_, Vol. IX, p. 323.

Sporangia gregarious, sessile, or short stipitate depressed, annulate, or at least umbilicate above, white or anon roseate, about .75 mm; stipe, when present, short, thick, black or dark brown! hypothallus none; columella none; capillitium strongly calcareous, an abundance of irregular white nodules burden the delicate net; spores dark sooty brown with a shade of purple by transmitted light, verruculose, 12-13 .

This species is recognizable at once by its regular, uniform, depressed, annulate or pitted sporangia, scattered evenly over the habitat of rotten leaves or wood. It suggests a didymium in its form and habit, but is near a badhamia. Colorado; _Bethel_, 1908.

18. PHYSARUM CONFERTUM _Macbr. nom. nov._

PLATE XV., Figs. 1, 1 _a_, 1 _b_.

1899. _Physarum atrum_ Schw., Macbr., _N. A. S._, p. 36.

1911. _Physarum atrum_ Schw., Lister, _Mycetozoa, 2nd ed._, p. 74.

Sporangia small about .2-.3 mm. in diameter, gregarious, confluent, cl.u.s.tered or heaped, dull violaceous brown; peridium thin, more or less transparent, generally limeless but sometimes lightly sprinkled with minute white flecks: capillitium scanty, the calcareous nodes small, rounded, elongate, white! columella none; spores violet-brown, distinctly warted, 10-12 .

Having been a.s.sured on information believed trustworthy that the Schweinitzian herbarium confirmed the ident.i.ty of the species before us, in the first edition of this work the form was listed as _P. atrum_ Schw. Meantime in the herbarium referred to, at Philadelphia the original type of _P. atrum_ still exists. My valued correspondent, Mr.

Hugo Bilgram, has recently given it careful study. It is a limeless _P.

didermoides_ (Pers.) R.! Small wonder we have had trouble! Exit _Physarum atrum_ Schw.

The species is not uncommon, especially eastward; has been generally ignored for reasons cited.

Distinguished from everything else by the color and small size of the heaped sporangia. It resembles some phase of _P. virescens_ where the sporangia are small and somewhat heaped or rather aggregated, and scantily supplied with lime; but in such case the lime is yellow and the spores are small.

This species has also been constantly referred to our confused _P.

cinereum_, _P. plumbeum_, etc., but Schweinitz, who certainly had seen _P. cinereum_ in Europe, since he cites it, under several forms, in the _Conspectus_, found the species in America and proceeded in Pennsylvania in December to find something else, very different as he thought, and in fact. He called this new discovery _P. atrum_, "beautifully _reticulate_", he says "like _P. cinereum_ but larger."

Most American students in an effort to keep faith with their pioneer mycologist, have taken cue from the specific name, looking for something _black_, heedless that in Pennsylvania almost any delicate thing has 'dark looks' in the middle of the winter! Berlese in Saccardo _Syll._ VII., p. 350, regarding _P. atrum_ as a synonym, writes for the black American specimens, _P. reticulatum_, emphasizing another Schweinitzian descriptive adjective. But _P. atrum_ Schw. has had place in literature to this hour.

19. PHYSARUM MELLEUM (_Berk. & Br._) _Ma.s.s._

1873. _Dydymium melleum_ Berk. & Br., _Jour. Linn. Soc._, XIV., p. 83.

1873. _Didymium chrysopeplum_ Berk. & C., _Grev._, II., p. 53.

1876. _Physarum schumacheri_ Spr. var. _melleum_ Rost., _Mon., App._, p. 7.

1892. _Physarum melleum_ Ma.s.see, _Mon._, p. 278.

1896. _Cytidium melleum_ (Berk. & Br.), Morg., _Jour. Cin. Soc._, p. 83.

1899. _Physarum melleum_ (Berk. & Br.), Ma.s.s., Macbr., _N. A. S._, p. 47.

1911. _Physarum melleum_ Ma.s.s., Lister, _Mycetozoa, 2nd ed._, p. 46.

Sporangia scattered, stipitate, globose, flattened below, clear yellow or honey colored; stipe short, about equaling the sporangium, pure white, somewhat wrinkled; columella small but distinct, white; hypothallus none, capillitium abundant, open, snow-white, with rather large angularly stellate nodes; spore-ma.s.s brown, almost black; spores by transmitted light, pale violet or lilac-tinted, almost smooth, 7.5-10 .

Easily distinguished by its white stipe, columella and capillitium in contrast with yellow peridial walls. _N. A. F._, 1395. Ma.s.see refers this number erroneously to _P. schumacheri Rost._ The description and specimen do not correspond. By that name the species has however, been hitherto known in the United States.

Eastern United States, common; rare west of the Mississippi.

Reported from Brazil, j.a.pan and the tropic islands round the world.

Portugal.

20. PHYSARUM CITRINUM _Schumacher_.

1803. _Physarum citrinum_ Schum., _Enum. Pl. Saell._, II., p. 201.

1911. _Physarum citrinum_ Schum., List., _Mycetozoa, 2nd ed._, p. 51.

Sporangia gregarious, scattered, globose, somewhat flattened below, pale yellow, citrine, stipitate; the peridium thin, covered almost completely with small calcareous scales; stipe stout, erect, fragile, tapering upwards, furrowed, opaque, arising from a small hypothallus which is anon continuous from one sporangium to the next; columella small, conical, yellow; capillitium a rather dense, delicate network, the calcareous nodules yellow, numerous, roundish, and generally small; spore-ma.s.s black; spores under the lens violaceous, almost smooth, about 8 .

This species seems to be rare in the United States. It resembles somewhat _P. melleum_, from which it is distinguished by its yellow stipe. _P. galbeum_ is a smaller form, and lacks the columella.

Rostafinski strangely confused the synonymy here, including even _P.

rufipes_ Alb. & Schw.

New England, Ohio, Colorado.