T RICH I ALES 237 



The distinguishing feature in this order is found in the peculiar 

 sculpture of the capillitial threads. This is suggested by the tubules 

 of Lycogala, though probably the resemblance is superficial only. 

 The individual threads, as in Trichia, are called elaters, from their 

 probable efficiency in spore-dispersal. 



As here limited, the order is coextensive with the Calonemeae 

 of Rostafinski, except that that includes in addition the genera Proto- 

 trichin and Dianema. The course of differentiation may be assumed 

 to start with Dianema, through the Perichaeiinceae to the Arcyriaceae 

 and again from the same starting-point through Prototrichia to the 

 T r ic Iliac ae. 



Key to the Families of the Trichiales 



A. Capillitial threads transverse to the sporangial cavity, attached usually 

 at each end, plain or only slightly roughened . . Dianemaceae 



B. Capillitium plain, papillose, or spinulose, often scanty, not netted, the 



threads sometimes attached by one end to the sporangium wall, 



Perichaenaceae 



C. Capillitium a distinct net, usually attached below to the sporangial 



wall ; sculpture various, not continuous spiral bands Arcyriaceae 



D. Capillitial threads transverse, fascicled, attached at both ends, but 



sculptured by well defined spiral bands . . Prototrichiaceae 



E. Capillitial threads typically free, sometimes more or less branched, 



forming a loose net attached below, characterized by definite spiral 

 bands, or sometimes by scattered rings . . Trichiaceae 



A. DIANEMACEyE 



Key to the Genera of the Dianemaceae 



A. Capillitial threads attached at one end, or free . 1. Margarita 



B. Capillitial threads attached at each end ... 2. Dianema 



1. Margarita List. 

 1894. Margarita Lister, Mycet., p. 203. 

 Sporangia sessile, the capillitium simple, hair-like, coiled. 



1. Margarita metallica {Berk. & Br.) List. 



Plate XVII., Figs. 



1838. Physarum metalHcum Berk. & Br., Mag. Zool. & Bot., I., p, 49. 

 Sporangia scattered or clustered, globose, or somewhat plasmodio- 

 carpous, .5-1 mm., sessile, coppery iridescent, the peridium thin, open- 



