PYREXIDIUM.] 



81 



Tribe III. PYRENIDIEI Xyl. ex Cromb. Journ. Bot. 1874, 

 p. 337 ; Flora, 1875, p. 103. 



Thallus maculate, radiately appressed ; cortical layer distinct ; 

 gonimic granules moniliformly coherent. Apotheeia pyrenoid ; 

 spores 4nae, septate, brown ; paraphyses scarcely any. Spermo- 

 gones unknown. 



A singular tribe, holding amongst the Collemacei an analogous place 

 to the Pyrenodei amongst the Lichenacei. In this respect the family 

 very appropriately closes with it; for the genus Obryzttm, with its 

 pyrenocarpous apothecia, is now 

 known to be entirely parasitic, and 

 must be removed. The Pi/renidiei 

 consist of a single genus with a sin- 

 gle species ; further research may 

 bring others to light. 



19. PYRENIDIUM Nyl. Flora. 

 1865, p. 210. Thallus minute, 

 stellato-divided, fibrillose, the 

 cortical layer cellular, distinct. 

 Apothecia innate, scarcely promi- 

 nent; spores oblongo-ellipsoid, 3- 

 septate, brownish ; paraphyses 

 slender, few or obsolete; hyme- 

 nial gelatine not tinged with 

 iodine. 



Having regard only to the thal- 

 lus, this genus might be supposed 

 to be allied to Leptoyium ; but the 

 form of the apothecia separates it en- 

 tirely from all the preceding genera 

 of the Collemei. There seems no 

 reason to doubt that the apothecia 

 really belong to the thallus and not 

 to a parasitic fungus. 



t'ig. -21. 



Pt/renidiiim actinellum Nyl. a. Thal- 

 'line filaments, x30. b. Transverse 

 section of a filament, x200. c. A. 

 f rustule of the cortex, X 350. d. Go- 

 nimia. e, e'. Vertical sections of two 

 apothecia (viewed under water), X 30, 

 with a small portion of crustose 

 thallus. /. Theca with spores, X 350. 

 g. Two spores, xoOO. 



1. P. actinellam Nyl. Flora, 1865, p. 210. ThaUus adnate, 

 thinly crustseform, thinly stellato-fibriliose at the circumference, 

 the fibrillae equally cylindrical, sparingly branched, but usually 

 effuse, and entirely covered by or almost entirely composed of 

 somewhat erect fibrillae, sordid- or dark-olive (I -(-wine-red). Apo- 

 thecia minute, scarcely prominent, almost entirely innate, the 

 pyrenium entirely black ; spores 0,020-24 mm. long, 0,008-9 mm. 

 thick. Carroll, in Journ. Bot. 1865, p. 286 ; Cromb. Lich. Brit, 

 p. 10 ; Leight. Lich. Fl. p. 36, ed. 3, p. 37. 



The thallus of this species (of which I give Nylander's emended 

 diagnosis) forms small maculae on the substratum, which are more 

 or less scattered, or at length confluent. When sterile it is externally 

 very similar to states of Leptoyium microscopicum ; but under the 

 microscope its fibiilloe are seen to be equally cylindrical, while in 



G 



