102 THE MYXOMYCETES 



of hyaline, limeless threads, the other calcareous throughout, or nearly 

 so, the meshes large and the threads or tubules broad; columella none; 

 pseudocolumella sometimes present. 



This genus was by Link established on purely external characters. 

 Rostafinski supplemented Link's definition by calling attention to the 

 peculiar character of the capillitium and to the microscopic characters 

 in general. The outer peridium is thick and strong, unlike the ordinary 

 structure in Physarum. Some physarums, however, have a very similar 

 outer wall; P. brunneolum, for instance, or P. citrinellum. In dehiscence 

 and structure there is also some resemblance to some species of Did- 

 erma, and by Persoon and Fries the common species was so referred, 

 but the capillitium is again definitive. 



A critical study of all these things really begins with Rostafinski. 

 Under his definition of the present genus P. albescens Ell. might well be 

 entered here. Such course at present would but increase confusion, 

 and until by future research the ontogeny of all these, and so their rela- 

 tionship, shall be more exactly known, the genus may be left with its 

 historic species, — monotypic. 



Leocarpus fragilis (Dickson) Rost. 



Mon. 132. 1875. 

 PL VII, Figs. 146, 147, 148. 



1785. Lycoperdon fragile Dickson, PL Crypt. Brit. 1 : 25. 



1795. Diderma vernicosum Pers., Ust. Ann. Bot. 15 : 34. 



1797. Trichia lutea Trentep., Roth, Cat. Bot. 1 : 230. 



1801. Lycogala parasiticum With., Br. PL 4 ed. 372. 



1803. Spumaria ramosa Schum., Enum. PL Saell. 2 : 195. 



1803. Physarum nitidum Schum., Enum. PL Saell. 2 : 205. 



1803. Physarum vernicosum (Pers.) Schum., Enum. PL Saell. 2 : 206. 



1804. Reticularia fragilis (Dicks.) Poir., Lam. Encycl. 6 : 183. 



1809. Leocarpus vernicosus (Pers.) Link, Mag. Ges. Nat. Fr. Berl. 3 : 25. 



1809. Leocarpus spermoides Link, Mag. Ges. Nat. Fr. Berl. 3 : 25. 



1817. Leocarpus atrovirens Fr., Symp. Gast. 13. 



1827. Leangium atrovirens Fr., Stirp. Femsj. 83. 



1827. Leangium vernicosum (Pers.) Fr., Stirp. Femsj. 83. 



1829. Diderma atrovirens Fr., Syst. Myc. 3 : 103. 



1837. Tripotrichia elegans Corda, Icon. Fung. 1 : 22. 



1849. Leocarpus ramosus Fr., Summ. Veg. Scand. 450. 



1921. Liceopsis jurensis Meylan, Bull. Soc. Vaud. Sc. Nat. 53 : 459. 



Sporangia gregarious or clustered, sessile or stipitate, globose, obovoid 

 or elongated, rusty or yellow, but occasionally deep reddish brown or 

 nearly white, shining; peridium opening at maturity in somewhat 

 stellate fashion; capillitium as described for the genus; stipe when 



