43 LINDSAY, ON ABROTHALLUS. 



saxatilis appears to grow after detachment from its base of 

 support ; and its peculiar shape seems due both to curling up 

 of the margins of the lobes, and to repeated and superimposed 

 epithalline growths from and upon the original nucleus. The 

 lobes or lacinise are smooth, shining, and of a light gray 

 tint. A few grayish soredia are occasionally scattered over 

 the surface ; but I have not noticed, in specimens kindly 

 forwarded to me by Sir W. C. Trevelj^an, nor in the specimen 

 contained in Leighton's ' Lich. Brit, exsicc.,' any of the re- 

 productive organs of the Abrothalli. 1 do not, however, 

 regard the absence of the latter as at all a disproof of the 

 lichen being developed in the way I have hinted ; for I have 

 already stated that it most closely resembles sterile forms of 

 the deformations of P. saxatilis above described. It is 

 perfectly possible, moreover, that lacinise or squamules 

 bearing the pycnides, spermogones, or even apothecia of the 

 Abrothalli, have been covered over and concealed by subse- 

 quent epithalline growths. " There is no good reason why 

 they shoidd not fructify,^^ says Berkeley in the ' Gardener's 

 Chronicle,' March 15th, 1858, p. 172; but if the view just 

 propounded of the nature and origin of these erratic masses 

 be correct, we should never expect to find on them the 

 normal apothecia of P. saxatilis, though we might have good 

 grounds for anticipating the occasional occurrence of the 

 pycnides or spermogones of the Abrothalli. The theories 

 hitherto started to account for their peculiar form do not 

 appear to me to be satisfactory, viz., that they have been 

 formed round the droppings of sheep or rabbits, as nuclei, or 

 that they have grown on the twigs of trees, whence they 

 have been subsequently detached. Berkeley and Babington 

 regard the erratic lichen in question as a form of Parmelia 

 ccesia, or one of the '^ short-lobed forms of the Parmelia 

 stellaris group ;" but Sir W. Hooker, Sir W. C. Trevelyan, 

 and Leighton consider it a form of P. saxatilis, and in this 

 opinion, though I had at first some difficulty in deciding, I 

 entirely concur. Further, there is a close resemblance 

 between this erratic species and various Lecanoras of a 

 globular form, and showing no point of adhesion, which have 

 at various times been described by travellers as suddeidy 

 covering, like manna, large tracts of country in Asia, and as 

 being eaten by cattle and by nomadic tribes of natives."^ 

 Such lichens are the Lecanora esculenta and affinis of Tartary 

 and Persia. I have not been fortunate enough to see 

 specimens of these interesting lichens; but I think it ex- 



* Fide the author's ' Popular History of British Lichnis ' fRccvo, TjoiuIdii, 

 1856), pp. 211 and 228. 



