Rostafinski placed this genus near the _Didymieae_ on account of the calcareous columella and the non-calcareous capillitium. On the other hand the structure of the capillitium and the iridescent simple peridium ally _Diachaea_ to _Lamproderma_ and the _Stemoniteae_; the only distinction being the calcareous stem. It is simply an intermediate genus to be placed here more conveniently than anywhere else in what is of necessity a linear arrangement.

=Key to the Species of Diachaea=

_A._ Stipe and columella white.

_a._ Sporangium cylindric 1. _D. leucopodia_

_b._ Sporangium globose.

i. Evidently stalked 2. _D. splendens_

ii. Stalk very short, 5 mm., conic.

O Spores warted 3. _D. bulbillosa_

OO Spores faintly netted 4. _D. subsessilis_

_B._ Stipe yellowish or orange 5. _D. thomasii_

1. DIACHAEA LEUCOPODIA (_Bull._) _Rost._

1791. _Trichia leucopodia_ Bull., _Champ. de la France_, Pl. 502, Fig. 2.

1825. _Diachaea elegans_ Fries, _Syst. Orb. Veg._, I., p. 143.

1875. _Diachaea leucopoda_ (Bull.) Rost., _Mon._, p. 190.

Sporangia rather closely gregarious, metallic blue or purple iridescent, cylindric or ellipsoidal, obtuse, sub-umbilicate below, stipitate; stipe short, much less than one-half the total height, snow-white, tapering upward; hypothallus white, venulose, occurring from stipe to stipe to form an open network over the substratum; columella thick, cylindric, tapering, blunt, terminating below the apex, white; capillitium springing from every part of the columella, of slender threads, brown, flexuous, branching and anastomosing to form an intricate net; spores in ma.s.s nearly black, by transmitted light dull violaceous, minutely roughened, 7-9 .

A very beautiful species; not uncommon in the eastern states; rare west of the Mississippi. Easily recognized, amid related forms, by its snow-white stem, a feature which did not escape the notice of Bulliard and suggested the accepted specific name. Fries adopted the specific name proposed by Trentepohl and wrote _D. elegans_, simply because to him the peridium was "admodum elegans."

The peridium is exceedingly thin and early deciduous; the stipe long persistent. The plasmodium, dull white, was observed by Fries at the beginning of the century; "morphoseos clavem inter myxogastres hoc genus primum mihi subministravit."

This species, as the diachaeas generally, affects fallen sticks and leaves in orchards and forests and even spreads boldly over the foliage and stems of living plants.

New England, New York, Pennsylvania, Maryland, Virginia, South Carolina, Ohio, Iowa, California, Canada.

2. DIACHAEA SPLENDENS _Peck._

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

1877. _Diachaea splendens_ Peck, _Rep. N. Y. Mus._, x.x.x., p. 50.

Sporangia gregarious, metallic blue with brilliant iridescence, globose, stipitate; stipe white, short, tapering upward; hypothallus white, venulose, a network supporting the snowy stipes; columella white, cylindric, pa.s.sing the centre, obtuse; capillitium lax, of slender, anastomosing, brown, translucent threads; spores in ma.s.s black, by transmitted light dark-violaceous, very coa.r.s.ely warted, 7-10 .

This is perhaps the most showy species of the list. The globose brilliantly iridescent sporangia are lifted above the substratum on snow-white columnar stalks; these are again joined one to another by the pure white vein-like cords of the reticulate hypothallus. The plasmodium may spread very widely over all sorts of objects that come in the way, dry forest leaves and sticks, or the fruit and foliage of living plants.

Closely resembling the preceding, but differing in the globose sporangia, it may be instantly recognized under the lenses by its coa.r.s.ely papillate spores.

Not common. New York, Pennsylvania, Ontario, Ohio, Iowa, Nebraska.

3. DIACHAEA SUBSESSILIS _Pk._

1879. _Diachaea subsessilis_ Pk., _Rep. N. Y. Mus. Nat. History_, x.x.xI., p. 41.

1894. _Diachaea subsessilis_ Pk., Lister, _Mycetozoa_, p. 92.

Sporangia gregarious or closely crowded, small, about .5 mm., dull iridescent-blue, greenish-gray, etc., globose or depressed-globose, short-stalked or nearly sessile; stipe generally very short, reduced sometimes to a mere persistent cone, white; columella obsolescent or reduced to white conical intrusion of the stipe; capillitium radiating from the stipe, brown, consisting of branching, anastomosing threads, paler at the tips; hypothallus very scanty or none; spores minutely warted, the papillae arranged in an irregular, loose net-work, violet-brown, paler under the lens, 10-12 .

This species is easily recognizable by its diminutive size and generally defective structure; i. e. it has the appearance of a degenerate or depauperate representative of some finer form. Besides the type, yet to be seen in Albany, Dr. Sturgis reports the species from Connecticut and from the Isle of Wight! A small gathering is before me from Colorado.

Every sporangium is borne upon a calcareous pedicel, very short indeed, but real. The _var. globosa_ referred to in the English text under _D.

leucopodia_ has not appeared so far as reported, on this side the sea, but even such variety could scarcely in the hands of a collector take the place of the form now under consideration.

Specimens of _D. subsessilis_ from Europe correspond remarkably with those described by Drs. Peck and Sturgis. Mr. Lister would have our species a synonym for _Lamproderma f.u.c.kelianum cracovense_ (Rost.) Cel.

Rare; from Connecticut to Colorado.

4. DIACHaeA BULBILLOSA (_Berk. & Br._) _List._

1873. _Didymium bulbillosum_ Berk. & Br., _Jour. Linn. Soc._, XIV., p. 84.

1898. _Diachaea bulbillosa_ Lister, _Jour. Bot._, x.x.xVI., p. 165.

1911. _Diachaea bulbillosa_ Lister, _Mycetozoa, 2nd ed._, p. 119.

Sporangia gregarious, globose, small, iridescent purple, stipitate; stipe conical, white, sometimes brown, half-a-mm., half the total height; columella clavate, white or brown; capillitium of purple-brown threads united to form a lax net; spores violet-grey, marked with scattered warts "6-8 in a row across the hemisphere", 7-9 .

Java, _Berkeley & Broome, op. c._ Toronto, Canada; cited here by courtesy of Miss Currie who gives the spores 7.8 .

5. DIACHAEA THOMASII _Rex._

PLATE V., Fig. 6, 6 _a_.

1892. _Diachaea thomasii_ Rex, _Proc. Phil. Acad._, p. 329.

Sporangia gregarious, more or less crowded, purple and bronze, iridescent, globose sessile or short stipitate; stipe, when present, very short, thick, tapering rapidly upward, orange; hypothallus orange, prominent venulose, continuous; columella ochre yellow, rough, cylindric, tapering upward to one-half the height of the sporangium, obtuse; capillitium lax, of slender brown rigid threads, radiating from the columella in every direction, anastomosing to form a loose, large-meshed network; spore-ma.s.s brown; spores by transmitted light violaceous, minutely, unevenly warted, 10-12 .

The peculiar orange color of the calcareous deposits in stipe and columella easily distinguish this species. The capillitium is also distinctive, rigid, simple, and comparatively scant, lamprodermoid. Rex calls attention to the fact that under low magnification the spores appear spotted; but the spots are occasioned simply by the closer aggregation, at particular points, of the ordinary papillae.

A southern species. All the specimens so far reported are from the mountains of North Carolina.

The specimens referred to under this name by Lister, _Mon._, p. 92, as coming from "Kittery, U. S. A." (Kittery, Maine?), are, no doubt, according to Mr. Lister's figures, _Comatricha caespitosa_ Sturgis. See under that species.

_C._ LAMPRODERMACEae

Sporangia distinct, generally gregarious, more or less spherical; capillitium developed chiefly or solely from the summit of the columella.