LEPTOGI0M.] COLLEMEI. 65 



concave, concolorous ; spores 4 8nae, plurilocular or variously sep- 

 tate, ovoid or oblongo-ovoid, 0,020-34 mm. long, 0,008-16 mm. 

 thick. Cromb. Jouni. Bot. 1885, p. 195. To this Nylander (in litt.} 

 refers Leptogium tetrasporum Fr. fil. Vet. Ak. Forh. 1864, p. 276. 



As observed by Nylander, /. c., this has externally the appearance of 

 Lecidea uliginosa Ach., from which it is far removed by the structure of 

 the thallus and apothecia. It is near the preceding species, from which 

 it is distinguished by the less-developed thallus and the smaller con- 

 colorous apothecia. In the British specimens the apothecia are few, with 

 the spores usually 4nse, ovoid, 0,027-34 mm. long, 0,013-16 mm. thick. 



Hah. On mortar of walls in a maritime district. Distr. Rare in the 

 Channel Islands. B. M. : Port Gorey, Island of Sark. 



4. L. pusillum Nyl. Mem. Soc. Cherb. v. (1857) p. 90; Syn. i. 

 p. 121. Thallus very minute, lobulato-granulose, thin, adnate, 

 olive- or greenish-brown. Apothecia minute, concave, elevated, 

 reddish, prominent in the thalline exciple, the margin of which is 

 concolorous with the epithecium ; spores ovoid or narrowed at either 

 apex, 3-4-septate, 0,018-26 mm. long, 0,008-10 mm. thick. 

 Cromb. Lich. Brit. p. 7 ; Leight. Lich. Fl. p. 30, ed. 3, p. 27. 

 Brit. Exs. : Larb. Caesar, n. 54. 



An inconspicuous plant, apt to be overlooked. Scarcely any of the 

 gonimia are moniliform. The British specimens are usually little deve- 

 loped and more or less effuse (form effusum Nyl.). The apothecia are very 

 small and somewhat scattered. 



Hob. On mortar of old walls in maritime districts. Distr. Local 

 and rare in the Channel Islands and in S. and W. England. B. M. : 

 St. Brelade's Bay, Island of Jersey ; St. Peter's Port, Island of Guernsey. 

 Shiere, Surrey ; Freshford, near Bath, Somersetshire ; Kemble, Glou- 

 cestershire. 



5. L. subtile Nyl. Mem. Soc. Cherb. v. (1857) p. 90 ; Syn. i. 

 p. 121. Thallus effuse, very minutely divided, somewhat laci- 

 niato-dissect or granuloso-crenate, dark- or brownish-green. Apo- 

 thecia minute, gyalectoid, pale-brown or reddish, the margin thin, 

 entire, subconcolorous : spores ovoid, 3-5-septate, with longitu- 

 dinal septules, 0,020-23 mm. long, 0,008-10 mm. thick. Mudd, 

 Man. p. 46, t. 1. f. 8 ; Cromb. Lich. Brit. p. 8 ; Leight. Lich. Fl. 

 p. 31, ed. 3, p. 29. CWZma subtile Sm. Eng. Fl. v. p. 213; Tayl. 

 in Mack. Fl. Hib. ii. p. III. Poly cUdium subtile Gray, Nat. Arr. 

 i. p. 4Ql.iLichen sultilis Schrad. Spic. (1794) p. 95 ; Dicks. Crypt, 

 fasc. iv. p. 28 ; Eng. Bot, t. 1008. 



The more distinctly laciniate thallus when fully developed, and the 

 much smaller and thinly margined apothecia, distinguish this from L. 

 tenuissimum, with which it agrees in its entirely cellular structure. The 

 spores also are smaller, with fewer loculi. The apothecia are generally 

 numerous and somewhat crowded. 



Hab. On cretaceous rocks, on the ground, rarely on the roots of old 

 trees, in upland districts. Distr. Pretty general, though not very com- 

 mon, in 8. and W. England ; rare in the Channel Islands, N. England, 



F 



