CHAPTER IX. Ecology

ECOLOGY

A. GENERAL INTRODUCTION 356

B. EXTERNAL INFLUENCES 357 a. Temperature b. Humidity c. Wind d. Human Agency

C. LICHEN COMMUNITIES 362

1. ARBOREAL 363 a. Epiphyllous b. Corticolous c. Lignicolous

2. TERRICOLOUS 367 a. On calcareous soil b. On siliceous soil c. On bricks d. On humus e. On peaty soil f. On mosses g. On fungi

3. SAXICOLOUS 371 a. Characters of mineral substrata b. Colonization on rocks c. Calcicolous d. Silicicolous

4. OMNICOLOUS LICHENS 376

5. LOCALIZED COMMUNITIES 378 a. Maritime lichens b. Sand-dune lichens c. Mountain lichens d. Tundra lichens e. Desert lichens f. Aquatic lichens

D. LICHENS AS PIONEERS 392 a. Soil-formers b. Outposts of vegetation