THE DETEKMINATIOX OF LICHENS IN THE FIELD 21 



IS. Ascus Avith S spores. Sp. 1-many-septate . . . Porina. 

 Ascus with many spores. Sp. 1-septate Thelopsis. 



14. Th. dark brown with whitish cephalodia and 



fertile tubercles each with 8-50 perithecia. 



^^^" t^i'f Lophothelium. 



Th. wanting. Perithecia on a lichen with 



blue-green algie 15. 



15. Sp. 1-septate, colourless Didymospharia (Ji). 



Sp. simple or 3-5-septate, colourless Obryznm i /;. 



Sp. 3-septate, brown Pyi'enococcus ( /) 



1(>. Algal cells blue-green, lli. with fertile tu- 

 bercles, each containing 8-50 perithecia. 

 On turfy ground Lophothelium. 



Algal cells orange or green. Th. often absent 



or almost so. On trees 17. 



17. Perithecial walls distinct. Algal cells 



Trentepolilia 18. 



Perithecial walls wanting or imperfect. Algal 



cells Tren tepoli lia or FalmeUa 19. 



18. Perithecia minute. Paraj^hyses confused or 



indistinct. Sp. 1-3-septate Melanotheca. 



Perithecia larger. Paraphyses unbranched, 



free. Sp. 1-5-septate and also muriform . Anthracothecium 



19. Algal cells PalmelJa, Sp. 3-5-septate and 



slightly muriform Mycoporum. 



M^dlceW^ Trentejwhlia. Sp. 1-3-septate... Mycoporellum. 



(a) Some Graphidinese (Table G) with minute thecia may be 

 confused with this group. Spermogonial conditions of other lichens 

 have been described as species of Verrncaria. A number of plants 

 which are now considered to be fungi were at first described as species 

 of genera belonging to Pyrenodine^. 



_ (i) Occasionally the perithecia are in small groups, but not really 

 joined together (e.g., Artlwpijrenia i^jrenasireUa). 



(c) Thelidium sparsuhim, Poh/blastia siihviridicans, Arfho- 

 pyrenia arenicola, and A. halodytes also have been described a.s 

 containing blue-green algal cells. 



{d) As in Graphidinese the th. is often developed beneath the bark. 



{e) Some species of Artliopyrenia {e.g., A. falhix) have the 

 pamphyses distinct and may be mistaken for species of Porina, but 

 the asci of the latter are more elongate. 



^ (/) The spores sometimes become brownish when old, may be 

 /-septate in A. pJatyreiiia and ^. cldorococca, 2i\\(\. are (i times as 

 long as broad in A. taijlori. A. cerasi has ±elliptical perithecia. 



{(/) L. epidermidis is usu. considered to be a fungus. 



(70 A fungus. D. pidposi is sometimes present on CoUema 

 pulposum, and other species are occasionally found on other members 

 of Collemacea?. 



(/) A doubtful lichen. 



c3 



