PHYSARUM 25 



2. Physarum (Persoon} Rost. 



1795. Physarum Pers., Ust. Ann. Bot., XV., p. 5 (in part). 



1801. Physarum Pers., Syn. Fung., p. 168 (in part). 



1829. Physarum (Pers.) Fries, Syst. Myc., III., p. 127 (in part). 



1875. Physarum (Pers.) Rost., Man., p. 93. 



NOTE. Prior to Persoon the Physamms were variously referred : Ly co- 

 per don, Spharocarpus, Trichia, etc. It seems unnecessary to quote the 

 synonymy further here. 



Sporangia plasmodiocarpous, aethalioid or distinct ; the perid- 

 ium usually simple, sometimes double, irregularly dehiscent, 

 more or less definitely calcareous ; capillitium a uniform irregu- 

 lar net, dilated and calcareous at the nodes, adherent on all 

 sides to the peridial wall. 



This large and cosmopolitan genus is readily recognized by 

 the characters quoted. It may be added that the capillitial 

 threads are always exceedingly delicate, probably tubular, but 

 never filled with lime throughout ; the peridium may be almost 

 nude or encrusted with lime, which where present is always 

 amorphous, never crystalline ; the sporangia when distinct may 

 be either sessile or stipitate, and the stipe in the latter case is 

 often hollow and charged with lime. In capillitium intermediate 

 between TilniadocJie and BadJiamia, since in the first the capil- 

 litial branching is limited and the calcareous deposits scanty, 

 while in Badhamia the capillitium is intricate and calcareous 

 throughout. 



As first set up by its founder, the genus included diverse 

 forms, only one or two of which would be included in the 

 genus as now limited. Persoon, however, was left to develop 

 the matter to suit himself, and in successive works gave, under 

 this generic name, more and more prominence to forms now so 

 referred. Fries, Syst. Myc., pp. 127 ct seq., still better establishes 

 the genus, though still including forms that, judging from 

 description, seem to belong elsewhere. As here used, the limits 

 of the genus are those set by Rostafinski. 



