20-4 THE JOTTRyAL OF BOTAXY 



NEW KARE OR CRITICAL LICHENS. 

 By W. Watson, B.Sc. 



(Continued from p. 111.) 



Evernia fiirfuracea form scohicina (Ach.) Nyl. On siliceous 

 wall Bwlch Gwyn (50). Form ceratea (Ach.) Nyl. On old wall, 

 Thwaite {Qb^. Both these forms are often confluent with the type 

 and intermediates. 



Parmelia perlafa auct. plur. Hue, in his Causerie sur les Par- 

 melia, uses names for this ])lant and its segregates which are not usually 

 followed by British lichenologists. His work is chiefly based on the 

 P. perlata of Acharius, but Lichen perlafus was previously used by 

 Linnieus, Hudson, Lightfoot, Withei'idge and other authors. 



F. trichotera Hue. This is the plant usually known as P. perlafa 

 in this country. Hue considers that P. perlata Ach. is not the same 

 plant as the"^ one usually known as P. perlata, differing from it 

 in some thalline characters and especially in the chemical reaction 

 when potash is followed by chloride of lime. In P. perlata Ach. p, 

 rosy tint is given to the medulla, whilst in P. trichotera the medulla 

 is unaltered. I have examined many sjiecimens from various British 

 localities, and the reaction is nearly always that of P. trichotera Hue. 



P. pilosella Hue is more or less synonymous with the subspecies 

 P. cilia fa Nyl. (Cromb. Br. Lich. i. p. 288), but is restricted to the 

 moi-e extreme forms. Many of the plants placed by British hchen- 

 ologists under P. ciliata NvL could not be placed with P. pilosella 

 Hue. 



P. perlata Ach. {sec. Hue). Medulla KC rosy. On rock and 

 tree near Ottei-ford (5) — form. nov. micropliijlla. On wall, Combe 

 St. Nicholas (5). This is a form wdth short lobes, those in the 

 centre being finely laciniate-lobulate and often sorediate. A similar 

 form is described under P. trichotera in Harmand's Lichens de 

 France. 



P. cetrata Ach. According to Hue and Harmand this is the 

 P. perforata of many recent authors. Rhizinse are present on 

 the under sui-face almost up to the margin, whereas in P. perforata 

 Ach. they are absent for some distance from the margin. — The form 

 ciliosa Hue (P. perforata form ciliata Nyl.) is less common than 

 the sf)rediate form (f. sorediifera Wain). On rock, Loch Gal, Kerrv 

 (T. Hebden). 



P. perforata var. Claudelii Harm. On rock, Horner Wood, near 

 Porlock (o). 



P. laevigata (Sm.) Ach. The reaction of the medulla to chloride 

 of lime is given as negative by Crombie. Harmand comments on 

 this and states that the medulla becomes a faint rose tint. Leighton 

 gives the colour reaction as red. I have examined a numl^er of plants 

 referred to this species and find that the reaction is usually negative. 

 The medulla of a specimen collected by Dr. Parsons from granite 

 rocks, Lustleigh Cleeve (8), had a pale-red reaction. Other specimens 

 with a negative colouration in the medulla, and of which I have 

 definite notes, were collected on rocks at Simonsbath (o), Harlech and 



