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 (6r. scyphulifernni^), 

 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 

 ( Chroolepus nmbrina) 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 epithecium. 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. 



