Rev. W. A. Leighton on the British Graph ideae. 445 



5. concolor, T. & B. ! Ardellae convex, of the same colour 

 with the thallus, prumose with a whitish powder. 



On ash and oak. Sussex ! Mr. Borrer. 



6. duhium, T. & B. ! Ardellse rather convex, lurid, dark pur- 

 plish, pruinose. 



Thallus subtartareous, slightly cracked and sometimes scaly, 

 of a cinereous or purplish hue. 



On ash and oak. Sussex ! Mr, Borrer, 



f. detriturriy T. & B. ! Ardellse depressed, lurid, dark purplish, 

 nearly naked, more or less stellate. 



Thallus nearly as in e, but rather thinner and more polished, 

 and seldom tinged with purple ; sometimes a little raised above 

 the ardellse, so as to form a sort of spurious margin. 



On hazel. Sussex ! Mr. Borr'er. 



7j. microstiffma, T. & B. ! Ardellse minute, solitary, depressed, 

 covered with whitish pruina. 



Thallus a very thin film, with a tinge of purple, sometimes 

 rather thicker and white. 



On ash in shady places. Sussex ! Mr, Borrer. 



6. astroideum. Ardellse rather large, in depressed, naked, 

 radiate or stellate clusters, subimmersed, or very slightly raised 

 above the thallus, dark reddish-black or full brown-black. 



Thallus either thin, smooth, and of a dull reddish hue, or 

 thicker, smooth, cracked minutely and copiously, of a pale 

 whitish-gray or cream-colour. 



On oak and ash. Ardingley, Michelgrove, and Charlton Forest, 

 Sussex ! Mr. Borrer. 



Plate VIII. fig. 40. a. Vertical section of ardella ; by sporidia. 



The following is the result of the examination of the authentic 

 specimens in herb, Borrer of the genus 



Spiloma, 



Spiloma spharale. — Specimens from Schleicher ! in herb. Bor- 

 rer, were composed of masses of roundish granules. 



Spiloma dispersum, Turn. & Borr. Lich. Brit. 32 ! ; E. Bot. 

 t. 2398; Hook. Br. Fl. 2. 165. 



The pulvinuli of this plant appear under the microscope to 

 be composed externally of oblong brown nearly opake bodies 

 wrinkled or with network on the surface, probably from internal 

 granules, supported on short articulated pedicels, from which 

 the slightest touch easily detaches them, and discovers under- 



