The North American Slime-Moulds Part 56

=2. Dictydium= (_Schrad._) _Rost._

Sporangia distinct, gregarious, globose or depressed-globose, stipitate, cernuous; the peridium very delicate, evanescent, thickened on the inside by numerous meridional costae which are joined at frequent intervals by fine transverse threads more or less parallel to each other, forming a persistent network of rectangular meshes.

The ribs or costae of the spore-case radiate from the top of the stipe and unite again at the top of the sporangium in a feeble, irregular net.

Schrader, _Nov. Gen. Pl._, p. 11, 1797, applied the name _Dictydium_ to all _Cribraria_-like species in which the calyculus was wanting. Fries follows this, _Syst. Myc._, III., p. 164. Rostafinski, _Versuch_, p. 5, _Mon._, p. 229, first correctly limits the genus and separates it from _Cribraria_. 1873-75.

A single species is widely distributed throughout the world,--

1. DICTYDIUM CANCELLATUM (_Batsch_) _Macbr._

PLATE I., Figs. 6, 6 _a_ and PLATE XIX., Figs. 1, 1 _a_, 1 _b_, 1 _c_, 2, 3.

1789. _Mucor cancellatus_ Batsch, _Elench. Fung._, II., p. 131.

1797. _Dictydium umbilicatum_ Schrad., _Nov. Gen. Pl._, p. 11.

1801. _Cribraria cernua_ Pers., _Syn._, p. 189.

1816. _Dictydium cernuum_ Nees, _Syst. d. Pilz._, p. 117.

1875. _Dictydium cernuum_ (Pers.) Rost., _Mon._, p. 229.

1893. _Dictydium longipes_ Morg., _Cin. Soc. Jour._, p. 17, in part.

Sporangia gregarious, depressed globose, nodding, the apex at length umbilicate, stipitate, in color brown, or brownish purple; the stipe varying much in length from two to ten times the diameter of the sporangium, attaining 5-6 mm., generally erect, more or less twisted and pallid at the apex, below dark brown, with hypothallus small or none; calyculus often wanting, when present a mere film connecting the ribs of the net; the net made up chiefly of meridional ribs connected at intervals by transverse parallel threads, above an open _Cribraria_-like network closing the apex and more or less rudimentary; the spores varying in color through all shades of brown and purple when seen in ma.s.s, by transmitted light reddish, 5-7 , smooth or nearly so.

This species in the United States is one of the most variable in the whole group. The extremes of such variation might easily const.i.tute types for several distinct species were it not that in all directions the varieties shade into each other so completely as to defy definition.

We have before us specimens purple throughout and short-stemmed; purple with stem long, pale and twisted at apex; brown, with the same variations; short-stemmed, with the apex of the stem pallid, and long-stemmed, with and without the same peculiarity. Morgan (_Cin. Soc.

Nat. Hist. Jour._, 1893) would set off the purple, long-stemmed forms as _D. longipes_, "stipe three to five times the sporangium," but here are forms in which the stem is ten times the diameter of the sporangium, which yet possess in all other particulars the characters of the short-stemmed forms. European forms also vary. Ma.s.see figures one type; Lister, one or two others; Rostafinski's figure indicates a taller form; Fries says, "Stipes elongatus, peridio quinquies et ultra longior." It seems reasonable to suppose that the variation is largely due to atmospheric conditions at the time of fruiting. The purple forms may be cases of arrested development, since the plasmodium appears to be in all cases purple, or at least they seem to represent those plasmodia which have failed of normal ripening. We may recognize two or three general types, distinguished primarily by color:--

a. _D. cancellatum cancellatum._--Sporangia clear brown or with only a purplish tinge, the stipe tapering upward, and in extreme cases perfectly white at the twisted apex. The stipe in length ranges from three to ten times the diameter of the sporangium. The reticulations of the net are generally small and the ribs numerous. This is the most highly differentiated, finished type of the species.

b. _D. cancellatum purpureum._--Sporangium dark, the purple tints predominating, the stipe tapering upward, more or less twisted at the paler, sometimes almost colorless, apex. The stipe ranges a little shorter than in the preceding variety, three to seven times the sporangium. The reticulations of the net are often coa.r.s.e, the ribs being fewer; the whole structure weak and showing signs of imperfect development.

The figures, 1, 1 _a_, 1 _b_, 1 _c, l. c._, ill.u.s.trate the ideal accomplishment in form (a). The color is a clear definite brown with no suggestion of purple anywhere. The stipes are three or four times the diameter of the sporangium, brown below, white above, and twisted to allow the sporangium to hang inverted. This is complete in every part; a definite bell-shaped calyx, widening into the cancellate receptacle, the margin constricted, and closed at last by the apical net, _cribrum_, sign of the order.

In form (b), the structure is similar but by no means so symmetrical and complete. The calyx often fails, or is present by obscure indications only. The cancellation is coa.r.s.er, the number of ribs fewer, the whole sporangium more or less globose; ferruginous or purple, the prevailing tint. Figs. on Pl. 1. are from the ferruginous type.

Figure 3 represents a beautiful thing; cup-less, ellipsoidal, delicate, of average size and in every way well-proportioned, clear rosy brown in color.

This may stand for a third variety; (c) _D. cancellatum prolatum_.

Common everywhere. The fruit appears in June on decaying logs and stumps of various species of deciduous trees, conifers, etc., the finest, and greatest variety, are from southern Missouri.

ORDER IV

=LYCOGALALES=

Fructification aethalioid; peridium membranaceous, tough, simple, without vesiculose with protoplasmic ma.s.ses, within gelatinous; the capillitium of cortical origin, consisting of irregular lobate or branching tubules, varying much in width, and marked by numerous corrugations, irregular warts or bands; spores minute, ashen or pallid.

This order includes but a single genus,--

=Lycogala= _Micheli._

1729. _Lycogala_ Micheli, _Nov. Plant. Gen._, pp. 216, 217.

1753. _Lycoperdon_ Linn. _Syst. Nat._, in part.

1794. _Lycogala_ Persoon, Romer, _N. Bot. Mag._, p. 87.

Micheli's description and figures, _Nov. Plant. Gen._, pp. 216, 217, Tab. 95, leave no doubt but that this ill.u.s.trious man had species of _Lycogala_ before him when he described the genus. His figure 1. no doubt portrays the second species in our present list. More recent writers, from Persoon down, have used Micheli's designation, but differed in regard to the limits to which the name should be applied. It is here used substantially as in 1729. Fries and, after him, Rostafinski make a mistake in quoting Retzius as writing _Lycogala_ (1769). Retzius wrote _Lycoperdon sessile; Kongl. Vetenskaps Acad. Handling, for Ar._ 1769, p. 254.

=Key to the Species of Lycogala=

_A._ aethalia irregularly globose.

_a._ Cortex minutely roughened or warted; about 12 mm. in diameter 1. _L. epidendrum_

_b._ Cortex smooth, size large 2. _L. flavo-fusc.u.m_

_c._ Cortex rough; diameter 6 mm. or less 3. _L. exiguum_

_B._ aethalia conical 4. _L. conic.u.m_

1. LYCOGALA EPIDENDRUM (_Buxb._) _Fries._

1721. _Lycoperdon epidendron_, etc., Buxb., _En. Pl. Hal._, p. 203.

1753. _Lycoperdon epidendrum_ Linn., _Sp. Pl._, p. 1184.

1829. _Lycogala epidendrum_ (Buxb.) Fries, _Syst. Myc._ III., p. 80.

aethalia solitary or cl.u.s.tered, depressed spherical, or, when crowded, irregular, olivaceous or blackish, minutely warted, 3-10 mm. in diameter, dehiscing irregularly, but more often near the apex; peridium thin, but tough and persistent, made up of numerous agglutinated tubules enclosing in their mashes peculiar cell-like vesicles; capillitium parietal, consisting of long, branching, and anastomosing flattened tubules extended inwardly among the spores, everywhere marked by transverse wrinkles, ridges, and warts, the free ends of the ultimate branchlets rounded, concolorous with the spores; spore-ma.s.s, when fresh, rosy, or ashen with a rosaceous or purplish tinge, becoming with age sordid or ochraceous, spores by transmitted light colorless, minutely roughened or reticulate, 5-6 .

This is not only a cosmopolitan species, but is no doubt, the most common slime-mould in the world. Found everywhere on decaying wood of all sorts, more particularly on that of deciduous trees. It has likewise been long the subject of observation. It is doubtless the "_Fungus coccineus_" of Ray, 1690, and the type of Micheli's genus as here, 1729.

The different colors a.s.sumed, from the rich scarlet of the emerging plasmodium to the glistening bronze of the newly formed aethalium, have suggested various descriptive names,--as _L. miniata_ Pers., _L.

chalybeum_ of Batsch, and _L. plumbea_ Schum. The peridium is by authors described as double. This is for description only. In structure the outer and inner peridium completely blend. The outer is predominately vesiculose, the inner more gelatinous. For discussion of the microscopic structure see under the next species.

Common. New England, west to Nebraska, South Dakota, Colorado, Was.h.i.+ngton, Oregon, California; Alberta to Nicaragua.

_Lycogala terrestre_ Fr., _Syst. Myc._, III., 83, appears to be a variety of the present species. In spores and capillitial thread the forms are indistinguishable; the difference is a matter of size, and to some extent, of the color of the wall. The specimens are a little larger, depressed and angular. The peridium is paler, smoother, though sometimes almost black, thin, ruptured irregularly. But the form and color of the peridium in the sporocarps of the older species vary much in response to external conditions; on a substratum affording scant nutrition the forms of fructification are minute; and in all cases, if maturity be hastened, the peridium responds in darker colors. Under more favorable conditions the wall is smoother and brighter.

2. LYCOGALA FLAVO-FUSc.u.m (_Ehr._) _Rost._

1818. _Diphtherium flavo-fusc.u.m_ Ehr., _Syl. Myc. Berol._, p. 27.

1829. _Reticularia flavo-fusca_ (Ehr.) Fries, _Syst. Myc._, III., p. 88.

1873. _Lycogala flavo-fusc.u.m_ (Ehr.) Rost., _Versuch_, p. 3.

aethalia solitary or sometimes two or three together, large 2-4 cm. in diameter, spherical or spheroidal, purplish-gray or brown, smooth, s.h.i.+ning; the peridium thick, simple but in microscopic section showing two or three successive layers; capillitium of abundantly branching, irregular, transparent tubules, marked by numberless warts and transverse rings or wrinkles, spores in ma.s.s yellowish gray, by transmitted light, colorless, smooth or only faintly reticulate or roughened, 5-6 .

This, one of the largest and most striking of the slime-moulds, is by students generally mistaken for a puff-ball. It occurs on stumps and rotten logs of various sorts in the Mississippi valley, more often affecting stumps of _Acer saccharinum_ L. The fructification, when solitary, about the size of a walnut, though sometimes larger; when cl.u.s.tered, the individuals are smaller. The form depends largely upon the place in which the fruit is formed. The plasmodic ma.s.s is so large that its form is determined by gravity. Thus on the lower surface of a log raised a little distance from the earth the aethalium is often pyriform. This fact did not escape Micheli. See _Nov. Plant. Gen._, Tab.