Fig. 8. Spores of _Rhizocarpon alboatrum_ to illustrate the
several-celled to many-celled and muriform, hyaline to brown type. X
760.

Fig. 9. Spores of _Rhizocarpon petraeum_ of the same type as those shown
in the last figure, but larger, and usually composed of more cells. X
760.

Fig. 10. A vertical section through an apothecium of _Lecidea
rupestris_: a, the hymenium, composed of asci and paraphyses; b, the
hypothecium; c, the mycelium, the cells of the algal host, and particles
of the limestone on which the plant was growing; d, the weak,
light-colored, covered exciple. X 79.

Fig. 11. A vertical section through an apothecium of _Buellia parasema_,
the thallus below, and a portion of the woody substratum: a, the
hymenium, composed of asci and paraphyses; b, the strongly developed,
dark colored exciple; c, the dark colored hypothecium; d, the thallus,
composed of interwoven hyphae, and enclosing cells of the algal host, a
portion of the woody substratum. X 79.

Fig. 12. One branched and one unbranched paraphysis of _Buellia
parasema_. X 450.

Fig. 13. An ascus of _Buella parasema_, containing 8 spores. X 450.

The figures were outlined with camera lucida and drawn on the
table, close to the base of the microscope, 100 mm. below the
stage. They were reduced one-half in making the plate. Figures 2,