TT^ C. Sturgis — Type- Specimens of Myxomyceles. 473 



cannot be certain of that fact. Albertini and Schweinitz failed to 

 realize the extreme variabilit}' of F. septica, Gmel., and their diag- 

 noses of species rest largely on external characters. They were 

 necessarily ignorant of those characters, sach as the size of the 

 spores, which serve to distinguish Peck's species from others of the 

 genus. A degree of certainty attaches to our knowledge of F. och- 

 racea, Pk., which cannot possibly attach to F. muscorum, A. & S., 

 so that, although there is a strong probability that the two names 

 refer to the same species, it does not seem wise to retain a name 

 based on mere probability. 



Phtsarella mirabilis, Pk. [Physarum mirahile, Pk.), Rep. 

 XXXIIl, p. 22, 1880. Bull. Torr. Bot. CI., IX, p. 61, 1882. The 

 type-specimen of this species requires no comment. It agrees per- 

 fectly with the published descriptions and so peculiar a species 

 could hardl}' be confused with anything else. Whether we choose 

 to call it Physarella ohlonga^ (B. & C.) Morg., or Physarella mira- 

 bilis, Pk., will depend upon which of the two general principles of 

 nomenclature we follow. 



DiDERMA FLAviDUM, Pk., Rep. XXVIII, p. 54, 1875, and Rep. 

 XXXI, p. 55, 1878. Professor Peck has very properly referred this 

 species to Physarion contextum, Pers. I mention it here under the 

 original name merely because neither Lister nor Macbride refers to 

 that name as a synonym of P. contextum, Pers. The specimen 

 requires but little comment. I have compared it with an authentic 

 specimen received from Mr. Lister and the two are essentially iden- 

 tical. The sporangia of Peck's specimen are smaller and of a more 

 greenish-yellow color than in the Lister specimen, and the spores are 

 somewhat lai'ger. Some of the sporangia in Peck's specimen, espe- 

 cially the elongated forms, show a false columella in the shape of a 

 dense, flattened aggregation of lime-knots occupying the median line 

 of the sporangium but entirely free from the base. It may be noted 

 that in both specimens the lime-knots of the capillitium are white 

 only by reflected light ; by transmitted light they are of various 

 shades of yellow. 



Chondrioderma crustaceum, Pk. {Diderma crustaceiim, Pk,), 

 Rep. XXVI, p. 74, 1873, Rep. XXXI, p. 56, 1878. This is an inter- 

 esting species on account of the confusion which exists regarding it. 

 Lister places it under C. globosum, Rost., on account of the smooth 

 outer wall, the strongly developed hypothallus, and the dark purplish- 

 brown, spinulose spores, measuring 10-14/a in diameter. Macbride, 

 however, describes the spores of C. globosum, Rost., as measuring 



