18 THE MYXOMYCETES 



KEY TO ORDERS OF THE MYXOGASTRES 



a. Spore mass black or deep violaceous, rarely ferruginous or pallid; capil- 

 litium always present b 



a. Spore mass usually brown or yellow, sometimes purplish or rosy, very rarely 



blackish brown ; capillitium present or absent c 



b. Peridium or capillitium, or both, calcareous Order PHYSARALES 



b. Peridium and capillitium usually limeless; lime 

 if present restricted to hypothallus, stipe and 

 columella Order STEMONITALES 



c. True capillitium none or scanty (except in genus 

 Alwisia); pseudocapillitium often present, of tubules 

 or perforated plates which sometimes fray out into 

 threads; spores pallid, brown or purplish Order LICEALES 



c. Capillitium thread-like, more or less distinctly sculp- 

 tured, parietal or free; spores pallid or yellow Order TRICHIALES 



The sequence is intended to suggest that the presence of lime indi- 

 cates less complete specialization and that the elimination of lime by 

 the Plasmodium at the outset, before fructification, is indicative of 

 higher rank. The circumstance that the excreted lime may sometimes 

 serve a protective purpose does not vitiate the general principle. 

 The differentiation reaches a climax in the sculptured capillitium of 

 the trichias. 



Order PHYSARALES 



Spores violaceous black in mass; violaceous or violaceous brown by 

 transmitted light. Capillitium typically delicate and thread-like, 

 sometimes charged with lime, in one genus tubular and calcareous 

 throughout. Peridium simple or double, usually limy. 



The presence of calcareous deposits, either in the capillitium or the 

 peridium or the stalk, often in all three, is the chief diagnostic char- 

 acter of the order. Elsewhere similar deposits occur in the genus 

 Diachea only, in this treatment placed in the Stemonitales, but by 

 Lister and others placed in the Physaraceas, and clearly intermediate 

 in its relationships. 



Two families: 



KEY TO FAMILDZS OF PHYSARALES 



Capillitium more or less calcareous, usually reticulate or anastomos- 

 ing in intricate fashion; calcareous deposits often affecting entire 

 fructification Physaracejs 



Capillitium non-calcareous, usually less intricate; calcareous de- 

 posits affecting the peridium only, or the peridium and the 

 stipe Dedymiace^ 



