30 COLLE.MACEl. [mAGMOPSIS. 



dark violet-blackish ; spores 1-septate, colourless ; liymeiiial gela- 

 tine not tinged with iodine. 



From Pifrenidium, with which it is comparable, this dilfers in having 

 the thallus pvreuopsoid and indeterminate ; while from Verriicarina, to 

 which it has some resemblance, it difters in the apothecia not presenting 

 a true pyreuium. The genus as yet includes only two species, of which 

 one has been detected in Britain. 



1. M. argilospila Xyl. ex Cromb. Grevillea, xv. (18S6) p. 10. 

 — Thallus scattered, subfurfuraceous, very thin, olive-black. Apo- 

 thecia innate, minute, pcridiura sufficiently thin, violet-black ; 

 spores 0,022-20 mm. long, 0,007-0 mm. thick ; paraphyses slender, 

 sparingly present. — Verrucaria argUospila Nyl. Flora, 1S74, p. 15. 

 Verrucaria arenicola Leigbt. Grevillea, v. (1877) p. 155 ; Lich. Fl, 

 ed. 3, p. 470. 



The plant spreads extensively over the substratum in small, scattered, 

 more or less distinct macidfe. In structure the thallus is densely and 

 minutely cellular, each cell containing a minute subglobose gonimiuin. 

 The apothecia in the specimens seen are numerous, and are more con- 

 spicuous where the thallus is semi-obliterated. 



Hub. On sandy and clayey soil in upland tracts. — Disfr. Local and 

 scarce, in W. England ; though it no doubt occurs elsewhere. — B. M. : 

 Shelton Hough, near Shrewsbury, Shropshire. 



Family II. COLLEMACEI Xyl. IMem. Soc. Cherb. ii. (1854) 

 p. 8 ; Syn. i, p. 88 (cfr. Cromb. Grevillea, v. p. 76). 



Thallus foliaceous, or fruticulose, or crustaeeous, turgid and 

 gelatinous when moist, black, brown, dark olive, leaden, rarely 

 glaucescent ; gonimia somewhat small, nakedly conjoined, monili- 

 form ; medulla not distinct, but confused with the gouimic la3-er. 

 Apothecia most frequently Iccanorine, occasionally biatorine, rarely 

 endocarpoid, bypothecium colourless ; spores 8na3, rarely numerous, 

 very rarely 4n!Te, ellipsoid, ovoid or fusiform, simple or septate, or 

 variously divided, colourless, very rarely brown. Spermogones 

 usually with jointed sterigmata, occasionally with simple sterigmata, 

 and short oblong spermatia. 



This family, as now limited by Xylander, comprehends plants which in 

 most essential respects are more closely related to each other than those 

 referred to it in his previous classification. " It consists of a higher type of 

 lichens than the Ephebacei, being superior in structure, and for the 

 most part in figure, -n-ith the gonimic granules not or scarcely ever simple, 

 but more or less (that is, two or several) moniliform (hdrmdgonimia, 

 Nyl.). The thallus also, when moistened, is more turgid, and though 

 still somewhat Algoid in external appearance, is almost always much 

 better developed." In regard to the anatomical structure of the thallus, 

 Nylander, in his observations on "gonidia &c." (Flora, 1877, p. 359), has 

 pointed out that (in the higher genera at least) the whole thallus is to be 

 regarded as one syngonimium. This syngonimitmi, he adds, in lift., ori- 

 ginates either from a single primitive goniniiuui, or from the coalescence of 

 several gonimia into tme syngonimic body. 



