LECAXOKA.] LECANO-LECIDKKI. 357 



Subgen. 4. PLACODTUM Xyl. Not. Siillsk. pro F. cfc Fl. F. 

 Forh. V. (186(5) p. 12(). — Thiillus radiating, usually cffigurate at the 

 circumference. Apothecia often at length subbiatorine ; spores Snso, 

 ellipsoid, polari-bilocular, usually with longitudinal tube, very 

 rarely simple or subsimple ; hymenial gelatine (especially the 

 thecae) bluish with iodine. Spermogones with shortly jointed 

 sterigmata, and straight, oblong or bacilliform spermatia. — Placo- 

 dium DC. Fl. Fr. ii. (1805) p. 377; Xyl. :Mera. Soc. Chcrb. iii. 

 p. 177. 



OoO ooo o O' 



• • . . •' ii i • ; J i ; •' .OO ■ ■•;;:• 



Fig. 61. 



Lecanora (Placodiitm) callopisnia Ach. — a. Vertical section of tliallii-', X 200. 

 b. Three spores, X 500. c. Sterigmata and spermatia, X 500. 



Known by the more or less radiose thallus (which is variously yellow, 

 very rarely whitish), by the usual mode of division of the spores, and by 

 the short avthrosterigmata. The spermogones are externally somewhat 

 prominent, with the Ostioles in the j^ellow thalli orange-yellow. 



9. L. falgens Ach. Lich. Univ. (1810) p. 437 ; Xyl. ex Hue, 

 Revue Bot. 1886, p. 21. — Thallus orbicular, submonophyllous, 

 adnate, opaque, laciniato-divided at the circum.fereiice, pale yellow 

 or citrine ; lacinia^ crenate or crenato-lobulate (K-(- reddish-purplish). 

 Apothecia small, plane or convex, orange-coloured, K-|- purplish, the 

 thalline margin concolorous, at length obliterated ; spores simple, 

 0,009-12 mm. long, 0,005-6 mm. thick. — Placodhnn fidgens Gray, 

 Nat. Arr. i. p. 447 : Mudd, Man. p. 131 ; Cromb. Lich. Brit. p. 45 ; 

 Leight. Lich. Fl. p. 178, ed. 3, p. 164. Squamana fidr/ens Sm. Eng. 

 Fl. V. p. 195. Lichen fidgens '6'w. X. Act. t'psal. iv. (1794) p. 246 ; 

 Eng. Bot. t. 1667 : Dicks. Crypt, fasc. iv. p. 2-lt.—Brit. Exs. : Larb. 

 CiEsar. n. 27; Lich. Hb. n. 296; Cromb. n. 155. 



From the simple spores tliis might he referred, as has often been done, 

 to subgenus Si^Mimaria. Its true p'ace, however, is shown by the 



