350 I'YKKNOCAUPKI [mYCOPORELLUM 



Thallus crustaceous, thin or obsolete. Algal cells Trentepoldia. 

 Perithecia compound with a dark-coloured outer wall (pcridium), 

 the different })erithecia not distinctly separated ; asci ellipsoid ; 

 paraphyses scanty or wanting ; spores 8 in the ascus, elongate, 

 septate, colourless or brownish. 



1. M. obscurum A. L. Sm. — Thallus thin, forming spots on 

 the bark. P(!rithecia compound, thickly scattered over the bark, 

 orbicular or angular ; the outer peridial wall developed over the 

 top, black, the lower wall colourless ; peiithecial walls indistinct ; 

 paraphyses scanty, indistinct ; spores 8 in the ascus, oblong- 

 clavate, 3-septate, halonate, the upper cell slightly larger, 

 0,015 mm. long, 0,005 mm. thick. — OpegrapJia ohscura Pers. in 

 Ust. Ann. Bot. vii. p. 32, t. 3, fig. 5, B (1794); 0. atra var. 

 ohscura Schau\ Enum. p. 155 (1850) ; Leight. in Ann. Mag. Nat. 

 Hist. ser. 2, xiii. p. 441, t. 8, tig. 37 (1854). Mycoporum obscurum 

 Almq. in K. Svensk. Vet.-Akad. Hand), xvii. n. 6, p. 8 (1880). 



Hah. On bark of trees.— 5. M. Will's Braes, Forfar. 



2, M. sparsellum A. L. Sm. — Thallus white, thin, deter- 

 minate. Perithecia compound, enclosed in a black prominent 

 rugose roundish or irregular peridium, colourless below ; para- 

 physes indistinct ; spores 8 in the ascus, ovoid, colourless or 

 faintly smoky-brown, 1-septate, rounded at the ends, slightly 

 constricted, 0,018-22 mm. long, 0,007-10 mm. thick. — Myco- 

 porum sparsellum Nyl. in Flora xlvii. p. 618 (1864) & in Ann. 

 Sci. Nat. ser. 5, viii. p. 343 (1867); Carroll in Journ. Bot. vi. 

 p. 101 (1868); Cromb. Lich. Brit. p. 106; Leight. Lich. Fl. 

 p. 405 ; ed. 3, p. 437. 



Eecorded with several other tropical and sub-tropical species only 

 from S.W. Ireland. The thallus of Lindig's specimen from 

 New Granada contains Trentepohlia algse, which, along with the 

 septate spores, indicates its position in Mycoporellum. 



Hah. On holly. — Distr. Rare in S.W. Ireland (Cromaglown, 

 Killarney). 



There are a number of specimens in the British Museum 

 classified under the genera Lepra7-ia Ach. (Lich. Suec. Prod. p. 5 

 (1798)), Spiloma Ach. (Meth. p. 9 (1803)), and Byssus Mich. (Nov. 

 Plant. Gen. p. 210 (1729) ), which have been specifically determined 

 by their collectors. These genera and species, generally accepted by 

 older lichenologists, are the early or imperfect conditions of crus- 

 taceous lichens, or sometimes of algae or fungi, most of them 

 indeterminable. They grow usually in moist or shadj^ situations 

 that favour irregular growth, while retarding the normal development 

 of thallus and fruit. 



