Sporangia discoidal or saucer-shaped, gregarious, stipitate, erect or nodding, grayish-white, the peridium thin, breaking irregularly and persistent; stipe subulate, striate, reddish brown, transparent; capillitium variable as above stated; spores pale violet-brown, spinulose or nearly smooth, about 9 µ.
In Mycetozoa, 2nd ed., the spores are described as "dark or pale purplish brown, spinose, spinulose or nearly smooth, 9–17 µ in diameter." This would seem too great a variation even in this protean species. The only specimens in our herbarium are from the Congo valley. The spores are pale and nearly smooth, as in Tilmadoche alba, and 9 µ. Spores 17 µ suggest immaturity; penultimate cell-division.
The synonymy above cited shows how this species has impressed careful students. Doubtless in every case the reference is correct, judging from the specimen each author had before him, although it is hard to see how Chondrioderma might have been suggested.
The species is evidently tropical, though reported from Europe.
4. Craterium Trentepohl
- 1797. Craterium Trentepohl, Roth, Catal., I., p. 224.
Sporangia more or less distinctly cyathiform, stipitate, the peridium generally plainly of two layers or even of three, opening at the top by circumscission more or less definite, or by a distinct lid, the upper part calcareous often to a marked degree, the lower, cartilaginous, long persistent as a vasiform cup containing the capillitium and spores, the calcareous nodes aggregating more or less to form a pseudo-columella.
This genus is distinguished from Physarum and Badhamia chiefly by the form of the sporangia and the method of dehiscence. The capillitium is in some specimens particularly, of the Physarum type; in others, like that of Badhamia. There are accordingly species that receive at the hands of different authors diverse generic reference as one feature or another in the structure is emphasized in the different cases. It is granted that it is hard to draw the line sometimes between forms in which the dehiscence is irregularly circumscissile and those in which the wall breaks without any regularity whatever, since, in all, the breaking up of the peridium usually begins at the top. Species here included will, however, offer little ambiguity.
Key to the Species of Craterium
| A. Dehiscence circumscissile or by the breaking up of the upper wall of the sporangium. | |||
| a. Sporangia violet or purple | 1. C. paraguayense | ||
| b. Sporangia yellow | 2. C. aureum | ||
| c. Sporangia white-capped. | |||
| 1. Sporangia obovoid or globoid | 3. C. leucocephalum | ||
| 2. Sporangia cylindric, elongate | 4. C. cylindricum | ||
| B. Dehiscence by a distinct lid. | |||
| a. Capillitium pale brown | 5. C. concinnum | ||
| b. Capillitium white | 6. C. minutum | ||