22 THE NORTH AMERICAN SLIME-MOULDS 



Key to the Orders of the Myxogastres 



Spore-mass black or violaceous, rarely ferruginous . . . Series A 



Spore-mass never black; usually some shade of brown or yellow, rarely 



purplish or rosy, etc Series B 



Series A 



1. Capillitlum present, delicate, thread-like; sporangia calcareous more or 



less throughout I. Physarales 



2. Capillitium present, thread-like, arising usually as anastomosing 



branches from a well-developed columella, which in a single genus 

 contains lime ; sporangia otherwise non-calcareous II. Stemonitales --'^ 



Series B 



3. Capillitium none, or very imperfectly developed; spores of some shade 



of brown, rarely purplish III. Cribrariales , '' 



4. Capillitium the inwardly produced irregular extremities of plates or 



tubules, which by their interweaving outwardly make up the aethalial 

 wall; spores pale, ashen IV. Lycogalales x-'^ 



5. Capillitium made up of more or less distinctly sculptured threads, pari- 



etal or free, simple, branched, or reticulate; spores commonly yel- 

 low V. Trichiales >^' 



This sequence is meant to convey the idea that the presence of lime 

 is indicative of differentiation less complete. That the Plasmodium 

 should at the outset eliminate, by refusing the unnecessary lime, is 

 indicative of higher rank than that the lime should be carried until 

 the last and then be crystallized out, or excreted by simple desicca- 

 tion. The circumstance that the excreted lime may sometimes serve 

 a protective purpose in the fruit, does not vitiate the general prin- 

 ciple. In Series B the differentiation reaches a climax in the sculp- 

 tured capillitium of the trichias. 



ORDER I 



PHYSARALES 



Spores violaceous-black. The capillitium usually delicate and 

 thread-like; peridium and capillitium, one or other or both, more or 

 less extensively surcharged with lime. Peridium simple or double. 

 Fructification various. 



