LICHEN. 



Lichen. 



735 



Adurua 



name is taken from the Greek w/rn<, branched, in al- 

 ' luslon to the ramification of the thallus. 



25. STICTA. Apalheria circular, thickish, adhering close- 

 ly to the thallus, to which they are attached by the 

 centre, while they are otherwise free ; gemmiparous 

 plate* flat, forming disks, encircled by borders of the 

 thallus, which project beyond them. Tliallim some- 

 what leathery and cartilaginous, foliaceous, forming 

 large lobes ; beneath, villose or woolly, and general- 

 h maikitl with pits or pores (cyphellae), and mealy 

 warts (aoredia). 



This genus takes in the Lichen pulmonarius, or lung- 

 wart moss, which is common on the trunks of old trees 

 in this country ; but neither the cyphellae nor soredia 

 are seen in that species. Lichen scrobiculatus, (verru- 

 oosus of Hudson,) and L. fuliginosus of Dickson, afford, 

 therefore, better examples of Sticta. It may be noticed, 

 that both the Sticta pulmonacea ami S. -srrobiculata are 

 promiscuously denominated aitrnm (oak-rag) by die 

 peasantry, in the lowlands of Scotland. Several spread- 

 ing species, which cover the huge stems of tropical trees, 

 also belong to this genus. 



26. PARHELIA. Apothrcia circular, somewhat urceolate, 

 membranaceoufi, fixed to the thallus by the centre, 

 and free beneath ; gemmiparous plate covering the 

 whole of the apothecium, and almost concealing it, 

 bent inward at the circumference ; within, in some 

 species of simple texture, in others celluliferous and 

 striated. Y'A-< / membranaceous or inclined to lea- 

 ther}-, foliaceou* and often stellated, lobed and laci- 

 niated ; generally with fibrils on the under side. 



This genus contains about sixty species, and includes 

 some of the largest and most beautiful of the lichen 

 tribe, and several of those which are employed by the 

 Scottish Highlanders to tinge the woollen-stuffs which 

 they manufacture. It is divided into three sections. 1. 

 Aooona, with a circular leather}- frond, divided into broad 

 flat lobes. Of this, Lichen glomuliferus of flura Scnlica 

 may be mentioned as an example, while at the same 

 time it may be referred to as an instance of the excel- 

 lent talent for description possessed by Lightfoot Li- 

 chen caperatus, sometimes used for dyeing wool of a 

 yellow colour, likewise falls under this section ; and to 

 it may be added, L. perlatus ; lartevircns or herbaceus 

 of Hudson ; oiivaceus ; and the common yellow lichen 

 of walls, L. parietinus. 2. Circinaria, with the thallus 

 of a membranaceous substance and stellated form. To 

 tin- division belong Lichen omphalodes and L. saxatilis, 

 which are very abundant in the Highlands of Scotland 

 and Wales, and are much used as dye-stuffs ; likewise 

 L. merabranaceus of Dickson ; L. plumbeus of Light- 

 foot ; L. fahlunemi.i and stygius, which are found on 

 the mountains of Scotland ; the very common L. stel- 

 and L. centrifugus of British writers, (Parmelia 

 , Ach.) 3. Phiftcia. with the thallus somewhat 

 tceous, and of a stellated form, but the extre- 

 mities of the segments appearing as if inflated. Lichen 

 phjrsodes, Lin. aptly exemplifies this section. 



87. BORRCRA. Apnthecia circular, shaped like small 



cups or pedicles ; gemmiparous plates forming disks, 

 surrounded and embraced by an elevated border of 

 the thallu*, which is bent inwards; within, furnished 

 w ith vesicles, or sometimes of simple texture. T/ial- 

 bu cartilaginous, branched, and laciniated, the lati- 

 nise generally naked and channelled below, often ci- 

 liated. 



This genus, named in honour of a distinguished Eng- Lichen, 

 lish botanist, Mr. Borrer of Sussex, (who, it is under- s "V^ 

 stood, has been long engaged in preparing, conjointly 

 with another eminent cryptogamist, Mr. Dawson Tur- 

 ner of Yarmouth, a Lichcnogrn}ihin Britannica,) is well 

 characterized by the beautifully fringed species L. cili- 

 aris and L. tenellus of British authors. 



28. CETRAHIA. Apothecia roundish, plano-concave, at- CettarU. 

 tached obliquely to the margin of the thallus, and 

 therefore loo=e beneath, elevated and bent inward at 



the circumference; gemmiparous plate surrounded 

 by a projecting border formed by the thallus ; with- 

 in, of simple texture, or slightly celluliferous. Thal- 

 lus membranaceous, and somewhat cartilaginous, fo- 

 liaceous, irregularly laciniated, smooth below. 



The well-known Lichen Islandicus affords an exam- 

 ple of this genus. To it also belongs L. nivalis, which 

 grows on the summit of Ben Lawers in Scotland, but 

 which has not there been found in fructification : from 

 Acharius we learn, that the targets or apothecia are flesh 

 coloured, with a finely scolloped border, formed by the 

 thallus. L. juniperinus and glaucus of Linnaeus are 

 likewise Cetrarise : The latter species, with the apothe- 

 cia in a perfect state, (in which condition it is rarely 

 found,) has been detected near Inverary, by a distin- 

 guished Scottish cryptogamic botanist, Mr. Robert 

 Maughan, senior. 



29. PELTIDEA. Apothecia circular, flat; gemmiparous Pelt'ulra. 

 plates wholly above the thallus, and situated on ap- 

 propriate small lobes, attached somewhat obliquely ; 

 surrounded by elevated borders formed by the thal- 

 lus ; within, of simple texture, or celluliferous. Thai* 



lut leathery or membranaceous, leaf-like ; beneath, 

 veined and woolly, with partial lobules bearing the 

 apothecia. 



This genus is well marked by the numerous small 

 lobes of the frond, but is named from the proportional- 

 ly large peltac or targets (apothecia) with which these 

 lobules are ornamented. The far-famed Lichen cani- 

 nus, or ash-coloured ground liverwort, affords an exam- 

 ple; and L. venosus, scutatus, horizontalis, and aph- 

 thosus of Linnaeus, likewise belong to it. 



30. NEPHROMA. Apolkecia kidney-shaped, flat ; attach- Ncphioma. 

 ed to tlie under side of the frond, and on proper 

 lobes ; embraced by a raised thallu s-border, except 

 at the interior side or base of the lobe ; within, of 

 simple texture, and striated. Thallut leathery and 

 membranaceous, leaf-like ; beneath, smooth, or only 

 slightly villose, with partial lobules producing the 

 apothecia. 



This genus is nearly allied to the preceding, being 

 distinguished chiefly by the reniform appearance of the 

 apothecium, or rather of the gemmiparous plate. It 

 includes L. arrticus and antarcticus of Linnaeus; and 

 may be exemplified in L. resupinatus of our own coun- 

 try, the trivial name of which is taken from the circum- 

 stance of the apothecia facing downwards. 



31. DUFOURBA. Apnthecia circular, terminal, supported Dufoure, 

 each by a tubular branch of the thallus, which forms 

 a border to it ; fixed by the circumference, beneath 

 free; gemmiparous plates forming plano-convex disks, 

 within of simple texture. Thallus membranaceous 

 and soft, branched, roundish, within fistular and cot- 

 tony. 



This genus contains only two or three species, and 



