184 



PLATE 54. 



Thelotrema lepadinum Ach. 



1. Natural size. 



2. Two apothecia and fragment of thallus magnified, a, raised por- 

 tion of thallus and substratum ; b, excipular fringe. 



3. Section of apothecium. 



4. Section of thallus. 



5. Paraphyses and spore-sac. 



6. Spores. 



5. Gyrostomum Fr. PL Homon. 268. 1825. 



This genus is represented by one species (G. scyfhuliferw>n) y 

 very simple in its structure, with well-marked and apparently con- 

 stant characters. 



As in the preceding, the thallus and apothecia begin to de- 

 velop below the surface of the substratum. The thallus, especially 

 the algae, remain almost entirely hypophloeodal ; only a few algae 

 ( Chroolej)us umbrina) exist, about which the slender hyphae form 

 a close network ; there is no distinction into layers. The alga- 

 bearing hyphal network extends between the separated cell-layers of 

 the superficial cork, never penetrating the intact cells of the sub- 

 stratum. 



The apothecia are quite small and semi-globose ; they begin their 

 development below the surface of the substratum but soon break 

 through, and about this time the apical pore begins to form ; it 

 increases considerably in size, so that at maturity the apothecia are 

 more or less urn-shaped. The hypothecium (perithecium) is black, 

 likewise the epitheciiim. The paraphyses are simple and consider- 

 ably gelatinized. 



The spores are multilocular, colorless, with a thick gelatinous 

 exosporium. 



This lichen is of southern range, occurring upon various trees. 



PLATE 55. 

 Gyrostomum scyphuliferum (Ach.) Fr. 



1. Natural size. 



2. Portion magnified. 



3. Section of apothecium. 



4. Section of thallus. 



5. Paraphyses and spore-sac. 



6. Spores, a, young spores; b, later stage; c, mature spores. 



7. Algae. 



