Rev. W. A.'Leighton on the British Graphidese. 269 



cuspidate aspect, and which renders a branched or divaricate 

 lirella of a subhastate form. Disk broad and open, more or less 

 pulverulent and pruinose, encompassed with a thickened, raised, 

 rounded, incurved, uniform and unbroken proper margin, curving 

 in a peculiar bold and striking manner. The different forms of 

 lirella seem to be so intermixed, even on the same specimen, as to 

 render any attempts to define varieties from the specimens before 

 me altogether hopeless. 



" No. 89. Opegrapha scripta, 7. pulverulenta '^ ! and " No. 90. 

 Opegrapha scripta, S. ahietina " ! in Mr. Borrer's copy of Schserer's 

 ^Lich. Exsicc' 1st ed., are, according to the sporidia, forms of 

 Gr aphis serpentina, Ach. Gr aphis pulverulenta, Ach., does not 

 appear to be represented in that work, and by consequence not 

 in Schserer^s ' Spicilegium Lich. Helvet.' nor * Enumeratio Lich. 

 Europ.' 



The sporidia are similar to those in Gr aphis scripta, Ach., 

 but the different character and habit of lirella, peculiar to itself, 

 well distinguish it from that species, whilst the sporidia separate 

 it from Gr aphis serpentina, Ach. It may be however considered 

 as very doubtful whether scripta and pulverulenta ought to be 

 retained as distinct species. 

 Plate VI. fig. 18. a, Vertical section of thallus and lirella; i, sporidium. 



3. Graphis serpentina, Ach. Thallus thin, membranaceous 

 or subtartareous, continuous, even or rugose; lirellse immersed, 

 slender, of the same width throughout, extremities obtuse ; proper 

 margin narrow, elevated, wavy and crisped; thallodal margin 

 elevated, tumid ; disk canaliculate, naked or pruinose ; sporidia 

 eight, in asci, linear, margined, rounded at the ends, containing 

 8-10 transversely oval margined yellow spores. 



Lichen serpentinus, Ach. Prodr. 25 (1798). 



Opegrapha serpentina, Schrad. Journ. d. Bot. 1801, st. 1. p. 79; Ach. 



Meth. 29. 

 Graphis serpentina, Ach. L. Univ. 269 (1810) ; Syn. 83 ; Fee, Crypt. Ecorc. 



Offic. Exot 40 (1824) ; pt. 2. p. 29. tab. .39. Graphis, fig. 20 (sporidia). 

 Opegrapha scripta, Schser. Lich. Exsicc. 87-91 inclus. 1st ed. (1823) ; ed. 



alt. immut. 87-91 inclus. (1842) ; Spicil. 46 & 322 (excl. syn. & var. C, 



r) & Sf) (1823-1836) ; Enum. 150 (excl. syn. & var. S). 

 scripta, c. serpentina. Fries, L. Ref. 371 ; Hook. Br. Fl. 2. 147 (in 



part). 

 Graphis scripta, Sprengel, Syst. Veg. 4. p. 1. 252. in part (1827). 

 pulverulenta, b.perihlastetica, Wallr. Crypt. Germ. 330 (1831). 



Plate VI. fig. 19. a, Thallus and lirella; b, sporidia — all magnified. 



The following varieties are to be observed : — 



a. minuta. Lirellse very short and simple, straight. 

 On young oak and ash. Sussex ! Mr. Borrer. Crafnant near 

 Oswestry, Shropshire ! Rev. T. Salwey. 



