J. A. MARTINDALE : NOTES ON BRITISH LICHENS. 



The preceding description is that of the form considered by 

 Dr. Arnold to be the type of the species. It is distinguished 

 from rnuroruni by the larger and more turgid th alius, often 

 forming rounded verrucose swellings and breaking out into 

 soredia, by the more oblong and larger spores, and by the 

 somewhat larger spermatia. Dr. Nylander has expressed 

 the belief that perhaps this is the true Lichen murorum of 

 Hoffman. States occur more or less different externally. 

 In one the thallus becomes effuse, or nearly so, the peri- 

 pheral lobes being very irregularly produced. In this state 

 the plant has a softer look, and a smoother surface, covered 

 slightly with a fine mealiness. In another state represented 

 by Rabh., Exs. 850, the thallus is not so turgid, hardly 

 verrucose, but breaking up into soredia here and there as in 

 the typical form. The spores are quite similar in all the 

 forms, and are peculiarly liable to deformations, being often 

 curved and sometimes narrower in the middle than at the 

 ends. The polar cells take on very irregular sliapes, each 

 being often nearly divided in two, and in extreme cases 

 the spore resembles that of Lecanora tetrastricha Nyl. 

 They are also sometimes simply uniseptate. 



I do not know whether the type occurs in Britain or not. 

 Leighton quotes Arnold, Exs., 382a, 382b as identical with 

 the plant he refers to decipiens, but neither of these numbers 

 is typical. He seems, furthermore, to have been guided 

 entirely by external appearance, not mentioning, in his 

 account of the species, the size of the spores nor describing 

 their shape correctly. The plant, referred to by Leighton 

 (I.e.), as gathered at Weston, in Oxfordshire, and presumably 

 the same as published by Larbalestier, Lich. Herb., No. 51, 

 is not decipiens at all, but tegula^is. I have gathered at 

 Shap, on limestone walls, a form which agrees fairly well 

 with Rabh., Exs., 850, or is intermediate between that and 

 the effuse state above mentioned. 

 Lecanora tegularis (Ehrh., Exs. 304 ; Hoffm., Flora Germ., 

 p. 158); Nyl., Flora, 1883, p. 106. Placodhim miniatimi 

 pro parte, Leight Lich. Flora, p. 162. Lecanora pusilla 

 Auctorum pro parte. 

 Thallus closely adnate, orbicular or broken and somewhat 

 dispersed, rimoso- or diffracto-areolate at the centre, plicato- 

 lobate at the circumference; lobes very short, convex, in- 

 cised or crenate, naked or albo- suffused, pale yellow, 

 vitellinous subminiate or miniate. 



Naturalist, 



