THE DETER. \rTXATT0T7 OF LTCIIEXS IN TTTE FIELD 19 



13. Ap. witli dark margin, longl)^ elliptical, form- 



ing little labyrinths of dark lines. Para- 



physes unbranclied. On wood Glyphis. 



Ap. immai-ginate, often oblong or elliptical. 



Paraph} ses branched. On wood or rock... 14. 



14. Hypothecium thick and black. Sp. colour- 



less, 2-many-septate. Th. not limited by 



a black line Chiodecton. 



Hypothecium colourless or with a thin black 

 line below. Th. often limited by a black 

 line. Sp. colourless or brown 15. 



15. Sp. colourless, 5-13-septate, 25-40 x 3-5 /x. 



Ap. minute. On trees or rocks Enterographa. 



Sp. dark brown, 4-7-septate, 20-25 x 5 /x. 



Ap. small. On rocks Sclerophy ton. 



(a) When the thecia are minute and little elongated they may be 

 confused with perithecia. 



(h) The ap. are minute and crowded together in specialized por- 

 tions of the th., which are not always wart-like. 



(c) Some plants belonging to Opef/rcqjJia and Arthonia have the 

 ap, crowded, but not on specialized portions of the th. 



(</) The ap. are sometimes roundish and may be mistaken for 

 those of plants with lecideoid ap. (Table I.). They are, however, 

 itdifform even in Lecanactis. The th. is often little visible and 

 developed beneath the bark. 



Some forms of Opegra])]ia, when the margin is practically absent 

 (e. g., O. atra var. artJionoidea, O. Tierpetica form arthonoidea) may 

 be mistaken for Arthonia. 



(<?) The rare L.flexella and L. dendographa occur on trees. 

 (/) X. parallela has its ap. arranged in parallel rows and can 

 thus be easily recognised. Some forms of Grapliis scripta, G. elegansy 

 and Opegraplia atra also have parallel ap., but they are usu. much 

 longer. 



(y) M. vermifera is parasitic on Pertusaria. 31. interjecta 

 occurs on rock, and is sometimes placed as a Litliograplia on account 

 of its dark hypothecium. M. patersoni is a peculiar species with 

 many-septate spores. 



(A) The spores of some species of Grapltis and Opegmpha may 

 become brownish w^hen old. The spores of PliceograpMs are colour- 

 less when young. 



H. ThALLUS CRUSTACEOUS (or wanting) with PERITHECIA 



(Pyeenodine.e) («). 



1. Perithecia simple and scattered (Z*) 2. 



Perithecia Hh united together 16. 



2. Algal cells (gonidia) green 3. 



Algal cells (gonidia) orange or reddish, usu. 



Trentepolilia 8. 



'Algal cells (gonimia) blue-green, or ap. para- 

 sitic on plants" with blue-green algae 14 ((?). 



