Arcyria. 141 



stipitate, peridia circumscised, upper part fugacious, spores 

 reddish fuscous. April 1850. S. C., H. W. R." 



The species was considered by Cooke to be Arcyria bicolor, 

 Berk. 



ARCYRIA, Hill (emended). 



Sporangia regular, plasmodiocarp, or aethalioid, wall single, 

 dehiscing irregularly or in a circumscissile manner, basal portion 

 persistent, columella absent ; stem usually filled with large cells 

 which become smaller upwards and gradually pass into normal 

 spores ; capillitium dense, usually becoming elastically elongated 

 and protruding during dehiscence, free, or the basal threads 

 attached to the inside of the stem, or attached at several points 

 to the lower, persistent portion of the sporangial wall, threads 

 combined to form a dense network with or without free ends, 

 ornamentation in the form of continuous ridges arranged in a 

 spiral, or prominent, plate-like half-rings or spines arranged in 

 a very open spiral, or wart-like spines scattered equally over the 

 entire surface of the threads. 



Arcyria. Host., Mon., p. 270 ; Cke., Myx. Brit., p. 69 ; Sacc., 

 Syll., vii., p. 425. 



Hemiarcyria, Host., Mon., p. 261 ; Cke., Myx. Brit., p. 67 ; 

 Mass., Mon. Trich., p. 27; Sacc., Syll., vii., 1, p. 446. 



The genus Hemiarcyria was founded by Rostafinski on those 

 species of Arcyria having continuous ridges arranged in a spiral 

 manner on the threads, as in the genus Trichia, and remodelled 

 Arcyria to include all those species having the threads orna- 

 mented in any other fashion than by spirally arranged ridges. 

 It is an open question as to whether ornamentation of the 

 capillitium threads is of generic value even if constant, as 

 supposed by Rostafinski, but such is certainly not the case; 

 the two extreme characteristics overlap and are combined in 

 several species. In some species of Hemiarcyria the spiral ridges 

 are accompanied by numerous spines, as in H. rubiformis and 

 H. serpula, whereas in H, melanopeziza, a Brazilian species, the 

 spines are abundant, and the spiral ridges present, but shadowy 

 in some individuals and entirely absent in others, consequently 



