DESCRIPTION OF THE PLATES.*

PLATE I.

Figs. 1 to 23. Comparative size of spores.

1. Pertusaria communis.
2. Opegrapha siderella.
3. Thelotrema lepadinum.
4. Aulacographa elegans.
5. Peltigera horizontalis.
6. Sticta scrobiculata.

7. Lecanora pallescens, var.
parella.

8. Graphis scripta.

9. Urceolaria scruposa.
10. Stereocaulon paschale.
11. Solorina crocea.

12. Physcia ciliaris.
13. Verrucaria nitida.
14. Lecidea geographica.
15. L. æruginosa.
16. Ramalina fraxinea.
17. Umbilicaria polymorpha.
18. Lecidea ferruginea.

19. Lecanora subfusca.

20. Parmelia parietina.
21. Usnea barbata.
22. Calicium hyperellum.
23. Cladonia pyxidata.

*The majority of the Illustrations are original. For the drawings of the spermogones and spermatia, pycnides and stylospores, and a few others, we are indebted to the Memoir of Tulasne. Several drawings illustrative of general characters or structure have been taken from the works of Leighton and

Fig. 24. Vertical section of a gymnocarpous apothecium.— a. Exciple. b. Thalamium.

25. Vertical section of an angiocarpous apothecium.-a. Exciple. b. Thalamium.

26-30. Germinating spores.

26. Lecanora pallescens, var. parella.

27, 28. Parmelia parietina.

29. Sphærophoron compressum.

30. Lecanora subfusca.

31. Vertical section of apothecium of Physcia ciliaris.—a. Paraphyses. b. Paraphyses acted on by iodine. c. Thecæ containing the spores, tinged blue by iodine. d. Hypothecium.

32. Gonidia.—a. Mature. b. In process of fissiparous division. c. Emptied of their contents. d. Nuclei or contents, after their escape.

33. Hypothallus developed around the spore of Cladonia extensa.

34. Gonidic mother-cells from young plants of Parmelia pa

rietina.

PLATE II.

1. Vertical section of apothecium and thallus of Parmelia parietina.-a. Tuberose extremities of paraphyses. b. Thecæ con

Schærer. In our own researches on the general or special microscopic anatomy of the Lichens, we have usually employed the magnifying power 380 of Nachet's (Parisian) microscope.

taining spores or protoplasm. c. Hypothecium. d. Gonidia. e. Medullary filaments. f. Cortical layer of thallus. g. Spore under action of iodine.

2. Spermogone of Parmelia ceratophylla, var. physodes.

3. Sterigmata of the same Lichen.

4. Spermatia, ditto.

5. Sterile spermogonal filaments, ditto.

6. Sterigmata and spermatia of Sticta pulmonaria.

7. Ditto ditto of Calicium turbinatum.

8. Ditto ditto of Lecanora atra.
9. Ditto ditto of Lecanora subfusca.
10. Ditto ditto of Urceolaria scruposa.
11. Sterigmata and spermatia of Lichina
12. Ditto ditto, of Ramalina fraxinea.
13. Pycnides of Scutula Wallrothii.
14. Sterigmata and stylospores of ditto.

PLATE III.

1. Usnea barbata, common form.

pygmæa.

2. Ditto, apothecium showing fibrillose-radiate margin. 3. Ditto, section of apothecium magnified.

4. Ditto, var. articulata, showing the inflated and articulated condition of the thalline filaments.

5. Ditto, var. plicata, also showing articulated condition of thalline filaments.

1. Cetraria aculeata.

PLATE IV.

2. Ditto, apothecium magnified. 3. Cornicularia ochroleuca.

4. Ditto, apothecium magnified. 5. Cornicularia vulpina.

6. C. jubata.

7. Ditto, apothecium magnified.

8. Ditto, spore.

9. Solorina crocea.-a. Upper, and b, lower surface.

10. Ditto, apothecium magnified.

11. Ditto, spore.

12. Solorina saccata.

13. Ditto, vertical section of apothecium.

14. Ditto, apothecium magnified.

15. Ditto, spores germinating.

PLATE V.

1. Roccella fuciformis, from Lima, South America,-" Lima (thin) Orchella-weed."

2. Roccella tinctoria, large variety from Lima.-" Lima (thick) Orchella-weed."

3. Ditto, small dark variety, neither warted nor very sorediiferous, from the Cape de Verde Islands.-"Cape de Verde Orchellaweed."

4. Ditto, small pale variety, very sorediiferous, also from the Cape de Verde Islands.

5. Ditto, portion of a thalline filament magnified, showing small, patellæform apothecia with a proper exciple, a; large, irregular apothecia, without a proper exciple, b; and soredia, c.

6. Ditto, portion of a thalline filament magnified, showing these forms of the apothecium sectioned.

7. Ditto, section of one of the small apothecia more highly magnified.

8. Ditto, portion of a pale-warted, thalline filament of the thickest "Lima Orchella-weed."

9. Ditto, transverse section of ditto.

10. Ditto, portion of a black-warted and geniculate thalline filament of the thickest "Lima Orchella-weed."

11. Ditto, spore.

12. Ditto, spermatia of a variety.

PLATE VI.

1. Ramalina fraxinea, large variety.

2. Ditto, section of mature and young apothecia, a; and of thallus, showing spermogones, b.

3. Ditto, section of a spermogone, showing sterigmata, spermatia, and network of filaments.

4. Ditto, spores of specimens from various habitats, in different stages of development, a being mature, 6 old, and the remainder young.