diderma] physaraceae 103 



threads, sparingly branched and anastomosing. Spores pale 

 violet-brown, nearly smooth, 6 to 8 /x diam. — Macbr. N. Am. 

 Slime-Moulds, 94. Physarum effustim Schwein. in Trans. Am. 

 Phil. Soc.,n.s. iv. 257 (1832). Didymium reticulatum Rost. in 

 Fuckel Symb. Myc, Nachtr. 2, p. 73 (1873). Chondrioderma 

 reticulatum Rost. Mon., p. 170 (1875) ; Mass. Mon., 216 ; Lister 

 Mycetozoa, 79 ; Petch in Ann. Perad., iv. 344. C. Saundersii 

 Berk. & Br. in litt. ; Mass. Mon., 209 (1892). Diderma 

 reticulatum Morg. I.e., 71 ; Macbr. I.e., 95. 



PI. 83. — /. orbicular and plasmodiocarp forms of sporangia (Philadelphia). 



The species published by Morgan as Diderma effusum, was so named 

 after it had been shown by Dr. Rex to be similar to the Schweinitzian 

 type of Physarum effusum. Morgan's graphic description leaves no 

 doubt that his specimens were the reticulate and effused form of the 

 present species, which has usually been distributed under the name 

 Chondrioderma reticulatum Rost. ; by the rule of priority Schweinitz's 

 specific name must be retained. Diderma effusum is closely allied both 

 to D. hetnisphericum (q.v.) and to D. testaceum ; from the latter it is 

 distinguished by the more frequent plasmodiocarp habit, the flatter 

 sporangia and the absence of any rosy tinge in the sporangium-wall 

 and columella. Ceylon gatherings, marked " 75. Diderma depressum 

 Fr." (B.M. 514 ; K. 1438, 1439), showing flattened white plasmo- 

 diocarps with brownish flesh-coloured columella, must be referred to 

 the present species ; so also must the type of Chondrioderma Saundersii 

 Berk. & Br. from Java (B.M. 1962), in which the flat plasmodiocarps 

 are effused over the under side of pinnules of a species of Adiantum. 



Hab. On dead leaves and twigs. — Flitwick, Beds (B.M. 1300) ; 

 Epping Forest, Essex (B.M. 2378); Wilts (B.M. 2381); Switzerland 

 (B.M. 2379) ; Germany (B.M. 2380) ; Portugal (B.M. 2383) ; Ceylon 

 (B.M. 514) ; Java (B.M. 1962) ; Japan (B.M. 2000) ; Ohio (B.M. 

 1302); New Hampshire (B.M. 1301); Iowa (B.M. 1022); Argentina 

 (B.M. 2382). 



4. D. spumarioides Fries Syst. Myc, iii. 104 (1829). 

 Plasmodium opaque white. Sporangia crowded, globose, 

 sessile, 0*5 to 1 mm. diam., smooth or rugose, white ; often 

 seated on a strongly developed white hypothallus ; sporangium- 

 wall of two layers, the outer thick, fragile, composed of globular 

 lime-granules 1 to 2 /a diam., more or less adhering to the 

 membranous inner layer. Columella convex or hemispherical, 

 white or pale flesh-coloured. CapiUitium consisting of slender 

 flexuose purplish threads, branching at an acute angle and 

 somewhat anastomosing. Spores violet-brown, spinulose, 8 

 to 11/i, diam. — Morgan Myx. Miami Valley, 67; Macbr. 

 N. Am. Slime-Moulds, 97. Didymium spumarioides Fr. 

 Symb. Gast., 20 (1818) ; Mass. Mon., 232. Reticularia 

 sphaeroidalis Bull. Champ., 94, t. 446, fig. 2 (1791) ? 

 Spumaria physaroides Pers. Syn., 163 (1801) ? Physarum 

 sphaeroidale Chev. Fl. Paris, i. 339 (1826) ? P. stromateum Link 

 Handb., iii. 409 (1833). Carcerina spumarioides Fr. Summ. 



G 2 



