PLATE 37 — Lichens. 



Figure 



1. Fragment of the thallus of Parmelia (PJiyscia) parietina, Ach., with young 



apothecia, and spermogonia, s, near the edges of the lobes. 



2. Vertical section of one of the spermogonia and the part of the thallus in which 



it lies. This section shows the upper and lower cortical layers of the thallus, 

 with the intermediate filamentous medulla and its globular gonidia. 



3. Fragment from the wall of the above spermogonium, more magnified to show 



the articulated filaments (spermatophores) which bear the spermatid. 



4. Spores of the same, treated with iodine ; the dark portion represents the proto- 



plasmic contents. 



5. A spore which has germinated. 



6. Fragment of a vertical section through the apotliecium of Parmelia (Physcia) 



stellaris, Fr. The upper part is the fertile layer, or thahtmium, b, composed 

 of thecal with spores, and paraphyses ; this rests on the hypothecium, h, beneath 

 which is a portion of the medullary layer, with gonidia, g. 



7. Ripe spores of the same. 



8. Ripe spores, germinated and not germinated, treated with sulphuric acid, and 



broken, showing the clear endospore inside the hard exospore. 



9. Ripe spore of Verrucaria nitida, Fr. 



10. Isolated spermatid from the spermogonia of ditto. 



11. Ripe spores of Peltigera horizontalis, Hoffru. 



12. Fragment of the thalamium of Sph&roplioron eoralloides, Pers., with ihecce in 



different stages of development, and free ripe spores. 



13. Vertical section of a spermogonium of Collema melcenum (Jacooca>folium), with 



spermatia escaping. Imbedded in the thallus are the moniliform gonidial 

 filaments. 



14. Isolated articulated filaments from the same. 



15. Isolated spermatia from these filaments. 



16. Vertical section of a spermogonium of Cladonia rangiferina, Hoffm., with sper- 



matia escaping from its orifice. 



17. Ripe spores of Urceolaria scruposa, Ach., seen in water. 



18. Fully developed spores of Umbilicaria pustulata, Hoffm. 



19. Ripe spores of Lecanora pardla, Ach. 





