Ohio, Illinois, Missouri, Iowa, Nebraska.
This species presents a decidedly well-marked form, so much so that it may be easily recognized at sight, without a lens. It therefore requires special discussion, and although in the spore-characters and some minor but not determinative details it agrees with P. virescens Ditm. to which it is by European authors sometimes referred, it seems nevertheless deserving of specific recognition, since in its entire habit and expression it is not only completely different but is constant in its specific peculiarities, much more so than is the suggested related form.
In the first edition of this work, the form was referred to Physarum thejoteum of Fries. This was the judgment of our American colleague, Professor A. P. Morgan whose work in this group is widely recognized. Fries admits, Syst. Myc., III., p. 142, that while he deems P. thejoteum very distinct, he yet has not seen P. virescens Ditm.! Since our form apparently does not occur in Europe, specimens which the distinguished author had before him were doubtless representatives of the now commonly recognized species of Ditmar.
For these reasons it seems appropriate to give the American type a suitably descriptive title.
17. Physarum megalosporum MacBr.
[Plate XVI.], Figs. 7 and 7 a.
- 1917. Physarum melanospermum Sturgis, Mycologia, Vol. IX., p. 323.
Sporangia gregarious, sessile, or short stipitate depressed, annulate, or at least umbilicate above, white or anon roseate, about .75 mm; stipe, when present, short, thick, black or dark brown! hypothallus none; columella none; capillitium strongly calcareous, an abundance of irregular white nodules burden the delicate net; spores dark sooty brown with a shade of purple by transmitted light, verruculose, 12–13 µ.
This species is recognizable at once by its regular, uniform, depressed, annulate or pitted sporangia, scattered evenly over the habitat of rotten leaves or wood. It suggests a didymium in its form and habit, but is near a badhamia. Colorado; Bethel, 1908.