192 THE NORTH AMERICAN SLIME-MOULDS 



the peridium ; peridium shining with metallic tints, deciduous, except 

 where, at the base of the columella, it forms a ring around the stipe ; 

 capillitium rising in tufts or by simple branches from the columella, 

 the threads regularly forked, generally united into a net. 



The lamprodermas are distinguished from the comatrichas, to 

 which they are most nearly allied, by the arrangement of the capil- 

 litium, its development from the apex only of the columella, the 

 continuation of the stipe within the peridium. In other words, the 

 peridium leaves the stipe some distance below the point where the 

 lowest capillitial branches take origin. In mature specimens the 

 peridium has often entirely disappeared, its only trace, a collar, more 

 or less distinct, around the stipe, marking the beginning of the colu- 

 mella. Nevertheless the peridium is far more persistent than in any 

 comatricha, and shows in yet greater brilliancy the wondrous metallic 

 tints and iridescence of Comatricha and Diachaea. Older authors, 

 so far as can be seen, distributed the species between Physarum and 

 Stemonitis. 



Key to the Species of Lamproderma 



A. Peridium metallic blue. 



a. Stipe short, stout. 



1. Capillitium tips colorless . . . 5. Z-. violaceum 



b. Stipe long, slender. 



1. Capillitium of dark, tapering, oft-united threads, 



3. L. columhinum 



2. Capillitial threads rigid, dark brown, seldom united, 



4. L. scintillans 



B. Peridium not blue, silvery. 



a. Stipe long, slender. 



1. Capillitium very intricate, forming a compact net, 



6. L. arcyrionema 



2. Capillitium of rigid dark brown threads 1. L. physaroides 



b. Stipe short, heads large, 1 mm. or more . 2. L. robustum 



1. Lamproderma physaroides (Alb. & Schw.) Rost. 



1805. Physarum physaroides Alb. & Schw., Consp. Fung., p. 103. 

 1875. Lamproderma physaroides (Alb. & Schw.) Rest, Mon., p. 202. 



Sporangia gregarious, wide-spreading, globose, the peridium per- 

 sistent with a silver metallic, sometimes brassy, lustre; stipe long, 

 brown or black, tapering upward ; hypothallus well developed, brown 



