98 Rev. T. Salwey -.List of the scarce Lichens found 



Collema velutinum, Ach. Upon ash-trees at Craig-y-Rhu. Dr. Tay- 

 lor refers this to nigrum. 



Solorina saccata. Wickliif Rocks, Ludlow : scarce. ' 



Peltidea venosa. Ditto. Ditto. 



P. scutata. On trees at Pentregaer, in fruit. 



P. horizontalis. Wickliff Rocks, Ludlow, Craigforda, &c. 



P. aphthosa. Craigforda, and woods at Downton Castle, Here- 

 fordshire. 



P. spuria. Dry banks at Oswestry, but very scarce. I do not 

 regard this as the same with venosa. If not a distinct species, I 

 should consider it with Fries a state of canina. Though about the 

 same size as venosa, the spuria is distinguished from it by not having 

 the thick dark-coloured veins underneath which that plant has, and 

 by the apothecia being smaller and narrower. In venosa they are of 

 a roundish shape and flat, something like those of horizontalis, but 

 of a dark colour like those of scutata. There is a Peltidea I have 

 occasionally met with, which I believe is regarded, if it has been no- 

 ticed at all, as the young state of canina ; it is however of much less 

 frequent occurrence than the canina, whilst the great difference in 

 habit and appearance inclines me to believe it to be a distinct one. 

 It is of an extremely thin and delicate texture, of a light bluish co- 

 lour, and grows in an imbricated manner, forming cushion- shaped 

 plants upon dry bare banks. The segments of the thallus are cir- 

 cular and inflexed, and the surface is copiously sprinkled by white 

 soft soredise. It has much the habit and appearance of Sticta lim.' 

 bata. Though I would not undertake to affirm that it is not the 

 young state of canina, I am inclined to think it is not. I am satis- 

 fied that a most patient and long-continued examination of parti- 

 cular plants in the same locality is required to enable us to clear up 

 many difficulties whicii make the study of the Lichens so perplexing. 



P. polydactyla. This is not so common as either rufescens or ca- 

 nina. I never saw it growing in such perfection as upon some 

 heaps of burnt turf upon a common which had been left for two or 

 three years before they were spread. I mention this because lichens 

 are generally considered to be, and certainly are usually, of very slow 

 growth, and yet here, where the turf on which they were growing 

 had undergone the action of fire, the plants were of a larger size 

 than usual, grew in the greatest profusion, and were copiously 

 fringed with apothecia. Now even admitting that the original ve- 

 getation upon these heaps had not been destroyed by the fire, but 

 that the plants in question escaped, still their unusual growth and 

 luxuriance were unquestionably influenced by the alteration the soil 

 had undergone. It has been suppposed however that lichens de- 

 rive their nourishment only through the media of air and light : 

 " Typicus lichenum omnium proventus est in acre et luce," says 

 Fries. I cannot but think however that in the instance now men- 

 tioned, the rapid growth and luxuriance of the plants must have 

 arisen from their deriving some nourishment through their roots, if 

 the fibres attaching the thallus to the soil may be so considered. I 

 have seen frequently an analogous case in the Hepatica, the old beds 



