82 COLLEMACEI. [PYREXIBIFM. 



L. vucroscopkvm they are unequal. In the few authentic specimens 

 seen, the apothecia are sparinjrly present ; and the other specimens, 

 referable to this or another species, are sterile. 



Hah. On cretaceous and calcareous pebbles in moist maritime and 

 upland districts, — Distr. A'ery sparingly in S. and S.W. England. — B.^I. : 

 Box Hill and r" Shiere, Sun-ey ; Pnear Brighton, Sussex; Anstey's Cove, 

 Torquay, S. Devon. 



Family TIT. LICHENACEI Xvl. Mem. Soc. Cherb. ii. 

 (lS5i) p. 10; Syn. "i. p. 141. 



Thallus polymorpbous, filamentose, foliaceous, squamose, crus- 

 taceous, pulverulent, or obsolete, or none, varying from mem- 

 branaceous to coriaceous and from filmy to tartareous, extremely 

 variable in colour, white, greyish, yellowish, reddish, brown, 

 blackish, but little or non-gelatinous ; gonidial layer usually 

 distinct, formed of true gonidia or rarely of gouimic granules. 

 Apothecia either stipitate or sessile, lecanorine, jiatellate, lecideine, 

 or pyrenoid, very variable in colour, but rarely concolorous with 

 the thallus. 8permogones either immersed or prominent, with 

 simple or articulate sterigmata and various spermatia. 



The plants belonging to this, by far the largest family of Lichens, are 

 very variable with respect both to the thallus and the fi-uctification. 

 They ditl'er from the precedins' families in being only very occasionally 

 gelatinous, and especially in having, except in a comparatively few 

 instances, a distinct stratum of bright green, rarely orange, gonidia. 

 The apothecia in most cases have the thalaniium furnished with para- 

 physes. which are generally distinct. In the lower genera some plants 

 approximate to the Ascomycetous Fungi. 



Series I. Epiconiodei Xyl. Syn. i. (1860) p. 141. 



Thallus either (1) horizontally expanded and crustaceous, some- 

 times none proper, with the apothecia usually stipitate, capilnliform, 

 occasionally sessile, or (2) fniticuloso-erect, with the apothecia 

 in terminal capitula of the thallus, nuclear, at length widely 

 open ; spores naked, usually collected into a pulverulent mass on 

 the surface of the mature fructification. 



Though in other respects varying considerably, the two tribes which 

 constitute this series agree in having the spores, except in a few species, 

 accumulated as a conglutinate powder or sporal mass (maza?diuni, 

 Ach.) on the surface of the mature fruit. It is only in the young 

 apothecia that the spores are seen in thec£e ; when more advanced, they 

 occur only free in the mazoedium. 



Tribe I. CALICIEI Xyl. Syn. i. (ISGO) p. 141. 



Thallus horizontal, crustaceous, granulose, or obsolete, or none 

 proper. Apothecia stipitate, capituliform, or sessile: spores 8na}, 

 in evanescent thecre, spherical or oblong, simple or variously septate, 



I 



