The North American Slime-Moulds Part 53

As to the habitat of the cribrarias, the remark of Schrader is still pertinent--"in vetustissimis plenariae destructionis proximis arborum truncis"--for all the species. Rotten, coniferous wood seems to be preferred, but the decayed logs of trees of other orders are by no means refused. Rotten oak forms a very common habitat.

=Key to the Species of Cribraria=

_A._ Sporangia with spores ochraceous or brownish.

_a._ Sporangia larger, .5 mm. or more.

1. Net poorly developed, sometimes merely indicated 1. _C. argillacea_

2. Net conspicuous, nodes expanded, not swollen.

i. Calyculus reticulately thickened, ill-defined above 2. _C. macrocarpa_

ii. Calyculus with radiant lines or ribs; net small-meshed; free ends none 6. _C. aurantiaca_

iii. Net wide-meshed, calyx rufous 4. _C. rufa_

iv. Calyx replaced by ribs 5. _C. splendens_

3. Net conspicuous, nodules swollen.

i. Net-threads simple; free ends many 7. _C. dictydioides_

ii. Net-threads often parallel in twos or threes 8. _C. intricata_

_b._ Sporangia small, less than .5 mm.

1. Nodes not expanded 3. _C. minutissima_

2. Nodes well shown.

i. Calyculus distinctly marked by radiant lines, nodes round 10. _C. tenella_

ii. Calyculus minute or none; nodes prominent 11. _C. microcarpa_

_B._ Sporangia more or less marked with purple or violet tints.

_a._ Purple or violet throughout.

1. Net poorly developed 12. _C. violacea_

2. Net well developed.

i. Meshes regular and the nodes distinct 14. _C. elegans_

ii. Meshes and nodules irregular 13. _C. purpurea_

_b._ Purple tints confined chiefly to plasmodic granules on the calyculus and stipe.

Net with nodes well expanded.

i. Stipe short, not more than double the sporangium; net and calyculus both well developed 9. _C. piriformis_

ii. Stipe many times the sporangium, weak 15. _C. languescens_

iii. Stipe slender, sporangium copper-colored 16. _C. cuprea_

1. CRIBRARIA ARGILLACEA _Pers._

PLATE XII., Figs. 12, 13; PLATE XVII., Fig. 1.

1791. _Stemonitis argillacea_ (Pers.) Gmel., _Syst. Nat._, II., 1469.

1796. _Cribraria argillacea_ Pers., _Obs. Myc._, I., p. 90.

Sporangia dull ochraceous-olivaceous, globose, nearly 1 mm. in diameter, sessile or short stipitate, closely gregarious or crowded, the peridial walls at maturity smooth, s.h.i.+ning, except above, long persistent, obscurely reticulate, with irregular thickenings which at the apex at length present the appearance of an irregular, coa.r.s.ely meshed net without nodal thickenings; stipe very short, stout, erect, reddish brown, spore-ma.s.s ochraceous, spores by transmitted light pale, spinulose, 5-6 .

This species stands just on the border-line between the tubiferas and the genus now before us. While on the one hand it possesses many characters such as the habit, form of sporangium, which are distinctly tubuline, on the other it shows in the upper peridial wall definite reticulations which suggest _Cribraria_. In freshly formed sporangia the reticulations are barely visible in the crown; later on they are more manifest, until, as spore-dispersal proceeds; the cribraria characters come out with sufficient distinctness, and in empty sporangia the reticulations may be seen to affect the entire peridial wall. The nodes are not expanded. The spores are pale by transmitted light, spinulose, about 6 . Plasmodium lead-colored. Found sometimes in large patches on rotten logs of various species. Not uncommon. Cf. _Lindbladia effusa_.

New England, New York, Pennsylvania, South Carolina, Ohio, Illinois, Iowa, Was.h.i.+ngton; Canada.

2. CRIBRARIA MACROCARPA _Schrader._

PLATE XVII., Fig. 2.

1797. _Cribraria macrocarpa_ Schrad., _Nov. Gen. Plant._, p. 8.

Sporangia more or less closely gregarious, yellowish brown, pear-shaped or obovate, large, .8-1 mm. in diameter, stipitate; stipe brown furrowed, erect or often nodding, about equal to the sporangium or longer; calyculus distinct, marked by numerous dark brown radiating ribs, iridescent, perforate above, deeply dentate, and merging gradually into the elegant network, of which the dark nodes are more distinctly expanded about half way up, less so at the apex and below, the filaments exceedingly delicate, simple, with occasional free ends projecting into the small meshes; spore-ma.s.s yellowish, spores by transmitted light almost colorless, minutely roughened, 5-6 .

Perhaps the most striking characteristic of the present species, aside from its large size, is the peculiarly perforated cup or calyculus.

Schrader's artist failed him here completely. The structure is exceedingly delicate, the peridium between the ribs and reticulations reduced to the last degree of tenuity, with the iridescence of the soap-bubble, here and there lapsed entirely. Withal the structure seems firm enough and persists until all the spores are dissipated by the wind.

Easily distinguished from the preceding, its only rival in size, by the obovate or turbinate, netted sporangium, its much longer stem, and flat, perfectly formed nodes.

Rare. New York, North Carolina, South Carolina, Oregon; Toronto, Canada.

3. CRIBRARIA MINUTISSIMA _Schweinitz._

PLATE XVII., Figs. 6, 6 _a_.

1832. _Cribraria minutissima_ Schw., _N. A. F._, No. 2362.

Sporangia scattered, orange or nut-brown, very minute, .1-.3 mm. or less, globose or ellipsoidal, stipitate, erect or nodding; hypothallus none; stipe short, 1-3 times the sporangium, filiform, tapering upward, brown; the calyculus variable, sometimes well marked and separated from the net when fully mature, by a shallow constriction, more commonly small or entirely wanting, especially in the spherical sporangia; net simple, large meshed, without nodal expansions, the threads flattened; spore-ma.s.s yellow, spores by transmitted light, pale, nearly smooth, 5-6 .

A most beautiful tiny species. Generally in all the specimens before us, a perfect, spherical net, firm enough to retain its place and structure after all the spores have been scattered. When mature the spore-ma.s.s seems to roll about as a ball, freely within the net, the spores being thus gradually dispersed. The calyculus when present is without veins.