222 THE MYXOMYCETES 



net; net made up chiefly of meridional ribs connected at intervals by 

 transverse parallel threads, an open Cribraria-like network above 

 closing the apex and more or less rudimentary; spores varying in color 

 through all shades of brown and purple when seen in mass, by 

 transmitted light reddish, 5-7 n, smooth or nearly so. 



Extremely variable, but the varieties grading into each other so 

 as to make attempted definition of slight value. There seems to be no 

 correlation, as some have supposed, between color and length of stipe, 

 but the more purple forms may be in part cases of arrested develop- 

 ment, since the Plasmodium appears to be always purplish. In the 

 typical form the sporangia are brown with only slight suggestion of 

 purple, the stipe from three to ten times the diameter of the spo- 

 rangium, tapering upward and paler to white at the twisted apex; the 

 reticulations of the net numerous, the meshes small. The following 

 varieties have been recognized: 



Var. purpureum Macbr., N. A. Slime-Moulds 173 (= Cribraria 

 exilis Macbr., Nat. Hist. Bull. Iowa 2 : 378, 1893). Cup often present, 

 reticulations coarser, color purplish throughout. 



Var. prolatum Macbr., N. A. Slime-Moulds ed. 2. 232, 1922. 

 Rosy brown, sporangium more erect, ellipsoidal, not at all com- 

 pressed. 



Var. fuscum Lister, Jour. Bot. 36 : 120, 1898. Dark brown, with a 

 well-defined cup. 



Var. alpinum Lister, Mycetozoa ed. 2. 185, 1911 (= Dictydium 

 anomalum Meylan, Bull. Soc. Vaud. 44 : 295, 1908; Dictydium mirabile 

 (Rost.) Meylan, Bull. Soc. Vaud. 57 : 305, 1931; Heterodictyon mirabile 

 Rost, Mon. 231, 1875; Cribraria mirabilis (Rost.) Mass., Mon. 60, 

 1892). Sporangia globose, erect, ribs 20-30, branching in upper third 

 of sporangium to form an irregular net; stalk not narrowed at apex, 

 often rugged. 



Var. anomalum Jahn, Ber. Deutsch. Bot. Ges. 19 : 99, 1901 

 (= Dictydium ambiguum Schrad., Nov. Gen. PI. 13, 1797). Ribs 

 branching and anastomosing to form a Cribraria-like net. 



Several of these variations are pictured on pi. XIX of N. A. Slime- 

 Moulds, 2nd edition. 



Common throughout the world, the fructifications often extending 

 for several feet. 



Family LICEACE^ 



Sporangia scattered, plasmodiocarpous, sessile or stalked, spo- 

 rangium wall cartilaginous or rarely membranous; capillitium lacking 

 or represented by a few thread-like processes. 



