CLASS XXII. ORDER V. 133 



covers entirely : frond crustaceous, indeterminate. 

 S7. 2 — chlorinuy (leprous-like lichen*) greenish 

 yellow or dark deep yellow, thick, effuse. 



Spiloma. Efflorescence in shapeless superficial 

 masses, woolly and powdery, rigid ; frond ciusta- 

 ceous mostly indeterminate, but sometimes border- 

 ed, thin and uniform. 57. 2 — melanc/ia^ (efflores- 

 cent lichen) blackish flat sub-confluent. 



B. Recefttacles^ comfiosed of a peculiar compact 

 hardish subsiancej not in any manner formed out 

 of the frond^ from vjhicJi it differs in^olourj be- 

 ing often black. 



1. Recefitacle ofien. 



Variolaria. Receptacles seated on a thick 

 tartarous crust, which supplies them with an acces- 

 sory border ; their disk is occupied with an assem- 

 blage of powdery substance : the frond is i^eneral- 

 ly determinate. This genus was supposed to have 

 no receptacle, until Dr. Smith detected the error. 

 57. ^—-fagineay (small-pox lichen) frond leprous 

 thin glabrous grey, receptacles white. 



Opegrapha. Clefts black, sessile, oblong or 

 linear, simple, confluent or branched, strait or zig- 



* Youi^g botanists who have not been informed to Nvhat 

 department of natui*e the word lichen applies, may be told, 

 that the following- substances are lichens. The spots on 

 rocks and stones which are white, yellow, black, &c. sprink- 

 led over with dots resembling fly-dirt upon window-glass. 

 Also the whitish green patches on old fences, trees, &c. and 

 the substance on trees of a fibrous structure and firm tex- 

 ture, usually called moss. It differs from moss in being 

 more tough and hard, and generally less gi'een. 



•f As the student will find nothing on lichens like those 

 organs denominated the fructification oPphenog-amous plants, 

 he may be told that by receptacles are here meant those 

 specks or dots mentioned in the last not^, or those saucer- 

 form substances on the large greenish pjttches on fences. 



