The North American Slime-Moulds Part 60

1829. _Lachn.o.bolus_ Fries, _Syst. Myc._, III., p. 177.

Sporangia distinct, sessile or nearly so, globose or cylindric, often distorted, scattered or densely crowded, the peridium extremely thin, ruptured irregularly, and persistent in fragments; capillitium attached at numerous points to the sporangial wall, forming a dense net, the threads warted or spinulose, non-elastic.

Species of this genus are easily distinguished from those of the next by the peculiar fragile peridium and the inelastic capillitium.

=Key to the Species of Lachn.o.bolus=

_A._ Sporangia pale yellow, on fallen flowers and fruit-burs of Castanea 1. _L. globosus_

_B._ Sporangia rosy or copper-colored, at length ochraceous 2. _L. occidentalis_

1. LACHn.o.bOLUS GLOBOSUS (_Schw._) _Rost._

1822. _Arcyria globosa_ Schw., _Syn. Fung. Carol._, No. 400.

1875. Lachn.o.bolus globosus (Schw.) _Rost., Mon._, p. 283.

1894. _Arcyria albida_ Pers. (in part) Lister, _Mycetozoa_, p. 186.

Sporangia on the spines of fallen chestnut burs, scattered, pale yellow or whitish, small, globose, the peridium early evanescent above, more persistent below, stipitate; stipe small, tapering upward, from a small hypothallus; capillitium a dense but not expanding network attached chiefly to the lower portion of the sporangial wall, minutely waited or roughened, with few expansions or inflations; spores in ma.s.s pale yellow, under the lens colorless, almost smooth, 7-8 .

This singular little species is remarkable chiefly in the habitat it affects,--fallen chestnut burs. On these almost universal, but on nothing else, except on the fallen catkins of the same species. Regarded by Mr. Lister as _A. cinerea_, from which it differs constantly in form, in capillitium more open and with larger threads, 4-5 in diameter as well as in its unique habitat, and yellowish color.

Distribution coterminous with that of _Castanea dentata_ Borkhausen,--eastern half of the United States.

2. LACHn.o.bOLUS OCCIDENTALIS _Macbr._

PLATE II., Figs. 2, 2 _a_, 2 _b_; 4 and 4 _a_.

1885. _Lachn.o.bolus incarnatus_ (Alb. & Schw.) Macbr., _Bull. Lab.

Nat. Hist. Iowa_, II., p. 126.

Sporangia scattered or crowded upon a hypothallus more or less distinct, globose or ellipsoidal, short-stipitate, varying somewhat in color, at first rosy or flesh-colored, later brownish or ochraceous; the peridium exceedingly thin, pellucid, mealy, evanescent above, persisting as a shallow cup below; capillitium inelastic, rather closely netted of threads variable in thickness, marked by frequent thickenings or expansions, everywhere warted, attached to the peridial walls, spores in ma.s.s flesh-colored, under the lens colorless, smooth, globose, 7.5-9 .

This delicate and elegant little species appears to be not uncommon, but is probably generally pa.s.sed over as an _Arcyria_, which it superficially resembles. When newly formed, the sporangia have a peculiar rosy or flesh-colored metallic tint, which is all their own.

Within a short time this color pa.s.ses, and most of the material comes from the field brownish or ochraceous in color. Typical sporangia are spherical on distinct short stipes; when crowded, the shape is of course less definite. The capillitium never expands as in _Arcyria_, but, exposed by the vanis.h.i.+ng upper wall, remains a spherical ma.s.s resting upon the shallow cup-like base of the peridium.

This species has been in the United States generally distributed as _L.

incarnatus_ (Alb. & Schw.) Schroet. A careful study of all descriptions of European forms and comparison of many specimens leads us to believe that we have here to do with a type presenting constant peculiarities.

We have in America nothing to correspond with the figures of Schweinitz, Berkeley, or Lister. In the American gatherings the sporangia are uniformly regular, globose, very generally short-stipitate, more or less closely gregarious, never superimposed, or heaped as shown in Berkeley's figure, for instance, _Ann. and Mag. Nat. Hist._, IV., xvii., Pl. ix., Fig. 2. The plasmodium of our species is white; as it approaches maturity a rosy metallic tinge supervenes, quickly changing to dull yellow or alutaceous. The graphic description given by Fries of _Perichaena incarnata_, _Syst. Myc._, III., p. 193, presents scarcely a character attributable to the form before us. _L. congesta_ Berk. & Br., evidently the form figured and described by Lister, _Mycetozoa_, p. 194, Pl. lxx., B., resembles our species in color and capillitium, but is entirely different in habit.

Not uncommon. Maine, Iowa, Missouri, Nebraska.

=2. Arcyria= (_Hill_) _Pers._

1751. _Arcyria_ Sir John Hill, _Gen. Nat. Hist._, II., p. 47.

1801. _Arcyria_ Pers., _Syn. Fung._, p. 182.

Sporangia ovoid or cylindric or even globose, stipitate; the peridium thin, evanescent to near the base, the lower part persisting as a calyculus; the stipe variable, packed with free cell-like vesicles, resembling spores, but larger; capillitium attached below, to the interior of the stipe or to the calyculus, in form an elastic network, the tubules adorned with warts, spinules, half-rings, etc., but without spiral bands or free extremities.

Micheli, of course, discovered the arcyrias, put them in two genera and several species, which we may only dimly recognize. Persoon first saw distinctly the outlines of the genus as now understood and adopted the name given by Hill in his curiously prolix description of certain species, probably partly of the genus _Arcyria_, partly _Stemonitis_.

=Key to the Species of Arcyria=

_A._ Mature capillitium loosely adhering to the calyculus.

_a._ Mature capillitium far-expanded, drooping.

i. Dusky.

O Long, 12 mm. or more 1. _A. magna_

OO Shorter, about 6 mm. 2. _A. oerstedtii_

ii. Yellow 3. _A. nutans_

_b._ Mature capillitium short, not drooping, though sometimes proc.u.mbent.

i. Capillitium greenish yellow 4. _A. versicolor_

ii. Capillitium reddish, flesh-colored, at length sordid, etc.

O Capillitium marked by transverse half-rings, cogs, etc. 5. _A. incarnata_

OO Capillitium marked by sharp-edged transverse plates and by numerous nodes 6. _A. nodulosa_

OOO Capillitium marked by close reticulations 7. _A. ferruginea_

_B._ Capillitium persistently attached to the calyculus.

_a._ Sporangia reddish brown, etc. 8. _A. denudata_

_b._ Sporangia gray or ashen

i. Simple 9. _A. cinerea_

ii. Cl.u.s.tered 10. _A. digitata_

_c._ Sporangia yellow 11. _A. pomiformis_

_d._ Sporangia rose-colored, .5-1.5 mm. 12. _A. insignis_

1. ARCYRIA MAGNA _Rex._

1893. _Arcyria magna_ Rex, _Proc. Phil. Acad._, p. 364.