414 



INTRODUCTION TO CRYPTOQAMIC BOTANY. 



remarkable for the round holes with which the disc is perfo- 

 rated. Lecanora is distinguished principally by its crust. 

 There are one or two genera separated from them on grounds 

 which interest the student of this particular class of Crypto- 

 gams, rather than the general reader. Urceolaria deserves 

 notice on account of its immersed, somewhat urceolate, discs, 

 which give the species an appearance very different from that 

 of the neighbouring Lecanorw. Fries does not think them 

 sufficiently distinct to justify their separation. Dirina is 

 remarkable for the carbonaceous stratum, from which the disc 

 springs. One or two species grow on trunks of trees in Spain 

 and the warmer parts of Em'ope, or the north of Africa. Oya- 



Rg. 87. 



a. Ascus with young half-formed spore of Sporopodium Leprieurii, 

 Mont., after Montagne, 



6. Vertical section of Coccocarpia smaragdina, from Cuming, No. 

 2154, showing the svib-hymenial tissue resting on the gonidia, the cor- 

 tical and medullary being altogether confluent. 



c. Ditto of Lecanora affinis. From Erzeroum specimens communicated 

 by Dr. Lindley. 



All more or less magnified. 



lecta has apparently a proper excipulum, but this is formed in 

 reality from the thallus, though differing in substance. The disc 

 easily falls out, and leaves the receptacle behind, which has a very 

 peculiar aspect, and is often mistaken for a Pe^^i^a. Lichen ex~ 

 anthertiaticus, which is referred doubtfully to this genus, occurs 



