LECANORA} LECANORACEE 265 
Hab. On calcareous and schistose rocks in maritime and upland 
regions.—Distr. Rather rare in W. England, Wales and Scotland.— 
B. M. St. David’s, Pembrokeshire ; Chance’s Pitch, Malvern, Wor- 
cestershire ; Barmouth, Merioneth ; Great Orme’s Head, Carnarvon- 
shire ; I. of Lismore, Argyll ; Craig Tulloch, Blair Athole, Perthshire. 
8. L. subimbricata A. L. Sm.—Thallus orbicular, closely 
adnate, crustaceous-arevlate in the centre, effigurate at the 
circumference, the outer radii contiguous, narrow and convex, or 
slightly broadening out and becoming plane and crenate at the 
tips, whitish or cinerous-grey (K + yellow, then red). Apothecia 
numerous, rather small, innate, then plane, brown or dark-brown 
when moist, almost black when dry, the thalline margin thin, 
entire ; paraphyses slender, constricted-septate ; spores broadly 
ellipsoid, 10-15 » long, 6-8°5 p thick.—L. circinata Ach. Lich. 
Univ. p. 425 (1810)? Hook. Fl. Scot. ii. p. 50; Cromb. Lich. 
Brit. p. 49 & Monogr. i. p. 403; Leight. Lich. Fl. p. 195 ; ed. 3, 
. 179; subsp. subcircinata Cromb. in Grevillea xvii. p. 47 
(1889). LL. subcircinata Nyl. in Flora lvi. p. 18 (1873). Lichen 
subimbricatus Relh. Fl. Cantab. p. 427, with fig. (1785). L. ear- 
cinatus Pers. in Ust. Ann. Bot. vii. p. 25 (1794?) ; Engl. Bot. 
t. 1941. Placodium circinatum 8. F. Gray, Nat. Arr. i. p. 448 
(1821). Squamaria circinata Hook. in Sm. Engl. Fl. v. p. 196 
(1833) ; Mudd Man. p. 130. 
In this species the paraphyses are septate and constricted, 
appearing almost like rows of conidia. In this respect both 
Continental and British species are alike, as is also L. circinatula. 
According to Nylander there is a difference in the reaction to potash 
between Continental and British specimens, the former failing to give 
the red colouration. I have found that a Continental specimen turns 
red, while some of our specimens remain yellow. Nylander did not 
consider that the reaction in this case was a specific distinction. In 
some specimens the apothecia and thallus have a reddish tinge 
(Parmelia circinata var. myrrhina Fr. Lich. Eur. p. 124 (1831). 
Lecanora circinata £. myrrhina Cromb. in Grevillea tom. cit. p. 47). 
The colour is, however, accidental, being caused by suffusion of 
peroxide of iron or by urine. Spermatia are recorded as 6-7 p long, 
1 » thick. An old specimen from Clare Hall Bridge, Relhan’s 
original locality, is in the herbarium of the British Museum. 
Hab. On rocks and walls, often on bridges, in lowland and upland 
districts.—Distr. Not common in the Channel Islands, England and 
Wales, reported from S.W. Scotland, not seen from Ireland—B, M. 
Guernsey ; near Staple Fitzpaine, Somerset; near Stroud, Gloucester- 
shire; Hale’s End, Malvern and Pershore Bridge, Worcestershire ; 
Oversley Bridge, Warwickshire; near Congerstone, Leicestershire ; 
Conway Castle, Denbighshire; Barnard Castle, Egglestone, and 
Teesdale, Durham; Kirkby Lonsdale, Westmoreland. 
Var. circinatula A. L. Sm.—Similar to the species in form, 
but rather darker and with smaller spores, 7 » long, 5 » thick.— 
L. circinatula Nyl. in Flora lxvi. p. 100 (1883); Cromb. in 
Grevillea xii. p. 89 (1884) & Monogr. i. p. 404. 
