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On Chemical Reaction in British Species of Pertusaria. 473 
A. variegatus that I should be sorry to make a new species 
out of it without further evidence. 
Dr. Gray gives no locality or other particulars concerning 
this specimen, simply stating that it has been “ received” b 
the British Museum. I may therefore add that it was ob- 
tained by the Hon. A. Gordon, lately Governor of Trinidad, 
from the upper part of the Caura river, a southern confluent 
of the Orinoco, and presented alive to the Society’s collection 
on the 14th of July last. It died on August 18th, and was 
sent to the British Museum. 
L.—Notulæ Lichenologicæ. No. XXXIV. 
By the Rev. W. A. Lxianros, B.A., F.L.S., F.B.S. Ed. 
Notes on the Chemical Reaction in the British species of 
IN preparing my * Lichen-Flora of Great Britain’ I have had 
occasion to devote a good deal of attention to the genus Pertu- 
saria, and have discovered that in no series of lichens do the 
chemical reagents give more important or more beneficial re- 
sults. By their means we are not only enabled to define the 
limits of the speciés themselves, but o definitely and satis- 
factorily to allocate the forms comprised in the old pseudo- 
genera of Variolaria and Isidium, which have ever proved a 
sort of crux to lichenists, and have consequently performed a 
continual migration from one genus to another. My proposed 
arrangement is as follows :— 
A. Thallus K yellow, then orange-red. 
1. P. multipunctata (Turn.), E. Bot. 2061. Variolaria 
multipunctata, T. & B.! Lich. Br. 73. 
2. P. Westringii (Ach.). P. lactescens, Mudd!, Man. 272. 
Isidium Westringtt, T. & B.! Lich. Brit. 93; E. Bot. 2204. 
3. P. glomerata (Schleich.). zs : : 
4. P. ceuthocarpa (Sm.), E. Bot. 2272.  Isidium microstic- 
ticum, 'T. & B.! Lich. Br. 94. a 
5. P. dealbata (Ach.), E. Bot. 1541 & 1511. Istdium pa- 
radoxum! and corallinum! and coccodes! a & B, T. & B. Lich. 
Brit. 97, 100, 89. Vartolaria chlorothecia, Tayl. ! Fl. Hib. 2. 
P. syncarpa, Mudd !, Man. 273. 
B. Thallus K yellow, C yellow. 
6. P. communis, DC., E. Bot. 677; and forma rupestris, 
