6 THE DETERMIXATTOX OF LTCHEXS IX THE FIELD 



Ap. with a tlialliiie margin. Squaiuules usu. 



imbricate 46. 



46. Til. lurid-brown or chestnut. Sp. 1-septate . 



Placolecania holophaea. 

 Th. pale, often yellowish. Sp. simple Squamaria. 



47. Sp. 1-septate and brown Physcia. 



Sp. simple and colourless 22. 



4S. On trees. Th. grey, often concentrically 



wrinkled. (Perithecia rare.) Normandina {q). 



On earth or rocks. Th. not concentrically 



wrinkle'd 49, 



49. Algal cells present in hymen ium. Sp. 



muriform Eiiiocarpon. 



Algal cells not present in hymenium. Sp. 



muriform Dacampia. 



Algal cells not present in hymenium. Sp. 



simple Dermatocarpon. 



50. Ap. on a slender black stalk and asci dissolving 



so that the spores are free. On trees and 



wood. Kare Chsenotheca (2 & 4). 



Ap. not stalked and asci not dissolving 51. 



51. Th. dark and ±gelatinous when moist. 



Algal cells (ISfostoc or _R/i' ?</(?;•/>/) scattered. 52. 

 Th. not gelatinous when moist. Algal cells 



in a detinite layer 54. 



52. Algal cells Bivularia. Very rare plant. Pterygium kenmorense. 

 Algal cells NostoG \ _ 53. 



58. Th. with cellular cortex. Sp.septate-muriform. Leptogium (>). 



Th. non -corticated. Sp. septate-muriform . . . C'' llama (1, 8 & 5). 



Th. non-corticated. Sp. simple Piiy^ma. 



54. Th. of ihiii^bricated yellow lacinise K — . Sp. 



many in ascus. Usu. on trees Candelaria concolor. 



Th. of yellow lacinise or lobes K+ purple. 



Sp. 8 m ascus Xa'ithoria. 



Th. usu. greyish or brownish, K+ or ~. 



Sp. 2-8. Usu. on rocks ^o. 



55. Th. having dark perithecia. Sp. muriform 



and large Polyblastia (11 & 17). 



Th. with dark perithecia. Sp. simple. Verrucaria macrostoma. 

 Thecia always open (apothecia). Sp. not 



muriform 56. 



56. Algal cells blue-green {Nostoc). Sp. usu. 



simple 57. 



Algal cells green. Sp. simple or septate 58. 



57. Ap. with thalline margin (usually crenulate). Pannaria (2-3). 

 Ap. without thalhne margin Parmeliella (2, 3, 5 ) . 



58. Th. yellowish, entirely cellular, K— ; algal 



ceils bright-green. Ap. with thalline mar- 

 gin. Sp. 8 simple. On mosses Psoroma hypnorum. 



Th. greenish-yellow withcitrine-yellow soredia Lecaiiora epanora. 



Th. not yellowish and not entirely cellular ... 59. 



