The North American Slime-Moulds Part 19

nefroideum_, _P. compressum_, _P. lividum_, etc.

The shadowy little species has had an eventful history, dipping in and out of our story in most uncertain fashion. Beginning with Fries, as noted, it received confirmation at the hands of DeBary, and by Rostafinski was given priority over a long list of synonyms, and figured. The earlier English authors follow Rostafinski, but for Lister in the _Mycetozoa_, p. 51, the species becomes a synonym of _T. alba_ as _P. nutans_, the description appropriately enlarged to receive it.

Meantime American students generally confused it with the tilmadoches on the one hand and _P. nefroideum_ R. (supposed) on the other. In 1897, Robt. Fries in _Sver. Myxom. Flora_, brings the species again to view as co-partner with _P. nutans_ and in the _Mycetozoa, 2nd ed._, p. 67, it appears as sub-species to the same.

The resemblance to _P. alb.u.m_ or _P. nutans_, is chiefly as intimated, a matter of definition; real differences are found in the irregular capillitium, fitting a globose sporange, in the character of the stipe and the consequent pose. See under _P. nutans_ and _P. notabile_.

34. PHYSARUM NODULOSUM _Cke. & Balf._

1881. _Physarum nodulosum_ Cke. & Balf., _Rav. N. A. F._, Exsic., 479.

1889. _Badhamia nodulosa_ Ma.s.see, _Jour. Myc._, Vol. V., p. 186.

1891. _Physarum calidris_ Lister, _Jour. Bot._, Vol. XXIX., p. 258.

1896. _Craterium nodulosum_ (Cke. & Balf.) Morg., _Jour. Cin. Soc._, p. 87.

1899. _Physarum nodulosum_ Cke. & Balf., Macbr., _N. A. S._, p. 51.

1911. _Physarum pusillum_ List., _Mycetozoa, 2nd ed._, p. 64.

Sporangia gregarious; minute, globose, bluish-white, the sporangial wall thin and more or less encrusted with lime, breaking up irregularly, stipitate; stipe slender, longer than the sporangium, attenuate upward or even, bright brown, rugose, expanded above into a shallow cup-like base for the sporangium; columella none; capillitium with lime-knots more or less abundant, white, often uniting, badhamioid; spore-ma.s.s black; spores by transmitted light, pale lilac-brown, almost smooth, 10-12 .

Pennsylvania, Ohio, Iowa; Canada.

One of the smallest species of the genus, by its proportionally long stipe and small round sporangium reminding one somewhat of _P.

globuliferum_; much smaller, however, and in every way different. The generic characters are mixed, and the species has been accordingly variously referred. The lower part of the peridium is sometimes persistent after the dehiscence, and so far reminds of _Craterium_. But this character is not constant, and even at best the persisting part is very small, not greater than in _P. melleum_, for example. On the other hand, the capillitium in some sporangia is strongly calcareous, reminds of _Badhamia_, but in most sporangia the _Physarum_ characters are sufficiently clear.

In the Kew Herbarium, it is said, are two American specimens under one label, "_Didymium pusillum_." One specimen is a didymium indeed, but, as it appears, _D. proximum_ Berk., already described. The other is a physarum. It is proposed in _Mycetozoa, 2nd ed._, to use the combination thus set free, as if applied by the original author to the second specimen, _not_ didymium, and to make the new combination date from 1873 and so take precedence of the binomial applied in 1881 by Cooke and Balfour here retained by the law of priority.

35. PHYSARUM MACULATUM _Macbr._

PLATE XIV., Figs. 6, 6 _a_, 6 _b_.

1893. _Bull. Lab. Nat. Hist. Iowa_, II., p. 383.

1899. _Physarum maculatum_ Macbr., _N. A. S._, p. 47.

1911. _Physarum tenerum_ Rex., Lister, _Mycetozoa_, p. 52, in part.

Sporangia scattered or gregarious, very small, .3-.4 mm., dull gray, thin-walled, dotted with minute, white calcareous granules, stipitate; stipe long, about 2 mm., stout, attenuated upward, striate longitudinally or wrinkled, filled with irregular yellow ma.s.ses of lime and accordingly bright yellow in color; columella none; capillitium forming a dense net, with comparatively small yellow nodular thickenings; spores globose, purplish, each minutely papillose and displaying several scattered spots occasioned by local development of the papillae; diameter of the spores 9-10 .

This species was set up for the reception of certain material collected by Professor Shimek, in 1892, in Nicaragua. It remains so far unique.

The small globose sporangium mounted upon a long upwardly tapering stipe, .5 mm. thick below, but narrowed at the extreme base where it is lightly attached, a stem which is simply a sack stuffed with yellow lime-granules;--this and the yellow capillitium are distinguishing features. The capillitium and spores suggest _Tilmadoche viride_, but the entire habit precludes such reference. Perhaps nearest to _P.

melleum_.

Castillo, Nicaragua.

Miss Lister thinks this the same as _P. tenerum_ Rex. But the whole habit and external appearance are different; the stipe notably long, clumsy, surcharged with lime; a very singular form.

36. PHYSARUM DIDERMOIDES (_Pers._) _Rost._

PLATE IX., Figs. 1, 1 _a_, 1 _b_, 1 _c_.

1801. _Spumaria (?) didermoides_ Acharius, Pers., _Syn. Fung._, p. xxix.

1829. _Diderma oblongum_ Fr., _Syst. Myc._, III., p. 103.

1831. _Spumaria licheniformis_ Schw., _N. A. F._, p. 261, No. 2364.

1832. _Physarum atrum_ Schw., _Syn. Fung., Am. Bor._, p. 258.

1875. _Physarum lividum_, Schw., Rostafinski, _Mon._, p. 96.

1875. _Physarum didermoides_ (Ach.) Rost., _Mon._, p. 97.

Plasmodium pale, watery-white or gray; sporangia crowded, ovoid or cylindric, stipitate or sessile, blue-gray, often capped with white; stipe variable in length and structure, where well developed pure white, often flattened, expanded and diaphanous, connate with others through the irregular reticulate or sheet-like hypothallus; columella none; capillitium ample, the lime knots angular or rounded, white connected by hyaline threads; spores in ma.s.s black, by transmitted light dark violet, decidedly spinulose, 12-15 .

A very variable species in many particulars. The sporangia in the same cl.u.s.ter are stipitate and sessile, ovoid and spherical. Our description does not quite agree with that of Rostafinski. As may be seen from the plate, it is the _outer_ peridium that is with us white, burdened with lime, the inner is simpler and comparatively thin. The whiteness of the outer peridium is however, easily displaced. The colony may not show it at all, in which case the peridia remaining give to the fructification entire a pale lead color, very characteristic. The disposition of the lime in the capillitium is also notably variable. Specimens occur which in so far realize Rostafinski's _Crateriachea_; that is, the lime is ma.s.sed as a snow-white pseudo-columella in the centre of each sporangium. In such cases the lime of the outer peridium is scant or limited in amount, never forming the calcareous cap shown in Fig. 1. The size of the spores is also variable. Rostafinski gives 12.5-14.2 ; not infrequently a single spore reaches 16 , a very unusual range of variation.

The species is not common in the upper Mississippi valley, but can be obtained in quant.i.ty where once it appears, as the plasmodia are profuse.

Ohio, Carolinas, Tennessee, Iowa, South Dakota, Kansas. Especially to be looked for on the bark of fallen stems of _Populus_ and _Negundo_.

Brazil, India, j.a.pan.

_Physarum lividum_ Rost., _Mon._, p. 95, is but a less calcareous form of this, as is evident even by the author's description. Professor Morgan thought _P. lividum_ a phase of _P. griseum_ Lk. Link, however, reckons _P. griseum_ the same as _P. cinereum_. Link, _Diss._, I., p.

27.

37. PHYSARUM LEUCOPUS _Link._

PLATE IX., Figs. 7, 7 _a_, 7 _b_.

1809. _Physarum leucopus_ Link, _Diss._, I, p. 27.

Sporangia gregarious, stipitate, globose snow-white, with a didymium like covering of calcareous particles; stipe white, not long, conical or tapering rapidly upward, slightly sulcate, brittle, from an evanescent hypothallus; columella none or small; capillitium, consisting of rather long hyaline threads, connecting the usual calcareous nodes, which are large, angular, snow-white; spore-ma.s.s black; spores by transmitted light, violet-brown, distinctly warted, about 10 .

The snow-white, nearly smooth stem, the small sporangium ( mm.) covered with loose calcareous granules, distinguish this rare species.

It looks like a small _Didymium squamulosum_. Fries called it _D.

leucopus_, _Syst. Myc._, III., p. 121.

Rare. Iowa, Ohio, Maine; Portugal.

38. PHYSARUM COMPRESSUM _Alb. & Schw._

PLATE XVIII., Fig. 14, and PLATE XIX., Fig. 12 and Fig. 4.

1805. _Physarum compressum_ Alb. & Schw., _Fung. Lus._, p. 97.

1875. _Physarum nefroideum_ Rost., _Mon._, p. 93, in part.

1875. _Physarum affine_ Rost., _Mon._, p. 94.

1909. _Physarum compressum_ Alb. & Schw., Torrend, _Fl. des Myx._, p. 197.

1911. _Physarum compressum_ List., _Mycetozoa, 2nd ed._, p. 70.

Sporangia more or less scattered, _compressed_-globose, or compressed-reniform, i. e. often umbilicate, stipitate, sessile, or elongate as if plasmodiocarpous, calcareous, white or ashen; peridium thin, covered with squamules, opening irregularly, usually by apical cleft; stipe, when present, short, stout, more or less sulcate, dark brown or ashen; capillitium a rather loose net, the nodules white, variable in size and shape; spores purplish-brown, delicately roughened, about 10-12.5 .

_P. affine_ R. was in this connection set up for European types compressed indeed, but more strongly _reniform_. The author says in his further description that the form _affine_ is less definitely umbilicate, has white stems, etc.; allantoid, one would now say. Such forms now begin to appear in America; and if for these a specific name is needed, it is provided, _P. affine_ Rost., Plate XIX., Fig. 4.