Sporangia stipitate, globose, or ellipsoid; columella cylindric or inflated or clavate at the apex, scarcely attaining half the height of the peridium; peridium shining with metallic tints, deciduous, except where, at the base of the columella, it forms a ring around the stipe; capillitium rising in tufts or by simple branches from the columella, the threads regularly forked, generally united into a net.

The lamprodermas are distinguished from the comatrichas, to which they are most nearly allied, by the arrangement of the capillitium, its development from the apex only of the columella, the continuation of the stipe within the peridium. In other words, the peridium leaves the stipe some distance below the point where the lowest capillitial branches take origin. In mature specimens the peridium has often entirely disappeared, its only trace, a collar, more or less distinct, around the stipe, marking the beginning of the columella. Nevertheless the peridium is far more persistent than in any comatricha, and shows in yet greater brilliancy the wondrous metallic tints and iridescence of Comatricha and Diachaea. Older authors, so far as can be seen, distributed the species between Physarum and Stemonitis.

Key to the Species of Lamproderma

A. Peridium metallic blue.
a. Stipe short, stout.
1. Capillitium tips colorless5. L. violaceum
b. Stipe long, slender.
1. Capillitium of dark, tapering, oft-united threads3. L. columbinum
2. Capillitial threads rigid, dark brown, seldom united4. L. scintillans
B. Peridium not blue, silvery.
a. Stipe long, slender.
1. Capillitium very intricate, forming a compact net6. L. arcyrionema
2. Capillitium of rigid dark brown threads1. L. physaroides
b. Stipe short, heads large, 1 mm. or more2. L. robustum

1. Lamproderma physaroides (Alb. & Schw.) Rost.

Sporangia gregarious, wide-spreading, globose, the peridium persistent with a silver metallic, sometimes brassy, lustre; stipe long, brown or black, tapering upward; hypothallus well developed, brown or purple, usually not continuous; columella swollen, obtuse, short at best, hardly attaining the centre of the sporangium; capillitium very rigid, of simple or sparingly branched, dark-brown threads radiating from the clavate apex of the columella and only here and there anastomosing toward the surface, the ultimate divisions distinctly rough; spores lilac brown, rough, 10–12.5 µ.

This species is well described and illustrated in Rostafinski's Monograph. It is well marked by its clavate columella and peculiarly simple, dark rigid capillitium, the branches of which rise in great numbers immediately from the columella, and maintain their primitive thickness during the greater part of their length. The transverse vincula are often at right angles to the principal branches, and the meshes, where formed, are often long and rectangular. Externally, it resembles L. arcyrionema, but is by its spores and capillitium instantly distinguished. Rostafinski gives the spores 12.5–14.2 µ. Large spores are less common in the specimens before us. Lister figures a sessile variety.

In our first edition this species was entered from lists published for New England, New York, and Ohio. The intervening years, however, have brought no confirmation. Specimens from Maine and Ohio, with large spores, represent L. columbinum, and those cited for New York are forms of L. violaceum. It is accordingly doubtful that L. physaroides (A. & S.) Rost. occurs in North America. That it is to be found in Europe there seems no doubt. The figure and description by Schweinitz, l. c., may indeed be inconclusive, but Rostafinski's citation and abundant description leave no doubt as to his opinion; while numerous localities named would indicate adequate material. What Rostafinski described will no doubt obtain wider recognition some day.