A HISTORY OF CORNWALL 



except in Jersey. One very rare species, Placodium fulgens, forms a zone 

 of a golden yellow colour on a calcareous sand dune near Padstow, and 

 also occurs on flat ground near Constantine Bay. 



The species common on old trees or old wood in drier countries 

 are remarkable for the absence of records, especially the genera Calicium 

 and Phlyctis. The species of the genus Pertusaria, though fairly repre- 

 sented, do not appear to fruit so freely as in the Devonshire ravines. The 

 Collemacei also, as might be expected from the absence of limestone, are 

 not very numerous. Where limestone does occur however, as at Cremyll 

 near Mount Edgcumbe, species characteristic of that formation, such as 

 Placodium cirrhochroum, Lecanora ochracea, L. ca/carea, Verrucaria immersa, 

 and V. conoidea, etc., are met with. The Gyropborei, which are fairly abun- 

 dant on the Dartmoor Tors, are represented in Cornwall very sparingly, 

 Umbilicaria pustulata and U. polyrrbiza only having been detected hitherto, 

 the former at St. Breward, Helmentor, and Tremoran Hill, and the latter 

 only near Helmentor. Lithographa dendrographa appears to occur much 

 more sparingly than in Devon, but Stigmatidium circumscription is notice- 

 able everywhere near the sea on the clay slate and the serpentine, 

 growing often in the most provoking manner across the grain of the 

 clay slate, so that it is almost impossible to get a good specimen. 



Although so large a proportion of the British lichen flora has 

 been detected in Cornwall, there is little doubt that many rare species 

 will yet be found on the maritime rocks and inland coppices, and possibly 

 on old trees in some of the parks scattered through the county. 



The classification followed is that of Crombie's British Lichens as far 

 as Urceo/aria and Leighton's British Lichen Flora from Lecanora to Melano- 

 theca, the species being arranged alphabetically for facility of reference. 



The rarer species in the list are indicated by an asterisk. 



EPHEBACEI, Nyl. COLLEMACEI (continued) 



Sirosiphon compactus, Ktttz. W.C. Collema plicatile, Nyl. E.G. 



Gonionema velutinum, Nyl. St. Cher, var. hydrocharum, Nyl. W.C. 



B.C. pulposum, Ach. W.C. 



Ephebe pubescens, Nyl. B.C., Rough Tor var. pulposulum, Nyl. B.C. 



Lichina pygmaea, Lightf. St. Minver, tenax, Ach. B.C. 



B.C. ; Penzance, Scilly Isles Collemodium biatorinum, Nyl. Wadebridge 



confinis, Ach. Antony, B.C. ; Fal- fluviatile, Nyl. St. Minver 



mouthy Penzance Schraderi, Nyl. 



COLLEMACEI turgidum, Nyl. Wadebridge 



Collema cheileum, Ach., f. nudum, Nyl. Leptogium amphineum, Nyl. Penzance 



B.C. lacerum, Gray, f. fimbriatum, Hoffm. 



concinnum, Flot. Penzance B.C. 



crispum, Ach. St. Minver sub-sp. pulvinatum, Nyl. Hayle Sands 



sub-sp. ceranoides, Nyl. St. Minver, sub-sp. lophasum, Nyl. B.C. 



Penzance Scotinum, Fr. Hayle Sands 



f. cristatulum, Nyl. St. Minver muscicolum, Fr. Penzance 



flaccidum, Ach. Boconnoc, Came/ford, palmatum, Mont. Marden Woods near 



St. Minver Penzance 



furvum, Ach. Forth Burrow subtile, Nyl. Withiel 



glaucescens, Hoffm. B.C. tenuissimum, Koerb. Penzance 



granuliferum, Nyl. St. Minver tremelloides, Gray. St. Issey, Ruan 



nigrescens, Ach. Lizard, Penzance Minor, Lamorna 



100 



