Chapter III: Morphology

I. GENERAL ACCOUNT OF LICHEN STRUCTURE

ORIGIN OF LICHEN STRUCTURES

A. FORMS OF CELL-STRUCTURE 67

B. TYPES OF THALLUS 68
_a._ Endogenous thallus
_b._ Exogenous thallus

II. STRATOSE THALLUS

1. CRUSTACEOUS LICHENS

A. GENERAL STRUCTURE 70

B. SAXICOLOUS LICHENS 70
_a._ Epilithic lichens
_aa._ Hypothallus or protothallus
_bb._ Formation of crustaceous tissues
_cc._ Formation of areolae
_b._ Endolithic lichens
_c._ Chemical nature of the substratum

C. CORTICOLOUS LICHENS 77
_a._ Epiphloeodal lichens
_b._ Hypophloeodal lichens

2. SQUAMULOSE LICHENS

A. DEVELOPMENT OF THE SQUAMULE 79

B. TISSUES OF SQUAMULOSE THALLUS 81

3. FOLIOSE LICHENS

A. DEVELOPMENT OF FOLIOSE THALLUS 82

B. CORTICAL TISSUES 82
_a._ Types of cortical structure
_b._ Origin of variation in cortical structure
_c._ Loss and renewal of cortex
_d._ Cortical hairs

C. GONIDIAL TISSUES 87

D. MEDULLA AND LOWER CORTEX 88
_a._ Medulla
_b._ Lower cortex
_c._ Hypothallic structures

E. STRUCTURES FOR PROTECTION AND ATTACHMENT 91
_a._ Cilia
_b._ Rhizinae
_c._ Haptera

F. STRENGTHENING TISSUES OF STRATOSE LICHENS 95
_a._ Produced by development of cortex
_b._ Produced by development of veins or nerves

III. RADIATE THALLUS

1. CHARACTERS OF RADIATE THALLUS

2. INTERMEDIATE TYPES OF THALLUS

3. FRUTICOSE AND FILAMENTOUS THALLUS

A. GENERAL STRUCTURE OF THALLUS 101

Cortical Structures
_a._ The fastigiate cortex
_b._ The fibrous cortex

B. SPECIAL STRENGTHENING STRUCTURES 103
_a._ Sclerotic strands
_b._ Chondroid axis

C. SURVEY OF MECHANICAL TISSUES 105

D. RETICULATE FRONDS 106

E. ROOTING BASE IN FRUTICOSE LICHENS 108

IV. STRATOSE-RADIATE THALLUS

1. STRATOSE OR PRIMARY THALLUS

A. GENERAL CHARACTERISTICS 111

B. TISSUES OF PRIMARY THALLUS 112
_a._ Cortical tissue
_b._ Gonidial tissue
_c._ Medullary tissue
_d._ Soredia

2. RADIATE OR SECONDARY THALLUS

A. ORIGIN OF THE PODETIUM 114

B. STRUCTURE OF THE PODETIUM 114
_a._ General structure
_b._ Gonidial tissue
_c._ Cortical tissue
_d._ Soredia

C. DEVELOPMENT OF THE SCYPHUS 117
_a._ From abortive apothecia
_b._ From polytomous branching
_c._ From arrested growth
_d._ Gonidia of the scyphus
_e._ Species without scyphi

D. BRANCHING OF THE PODETIUM 119

E. PERFORATIONS AND RETICULATION OF THE PODETIUM 120

F. ROOTING STRUCTURES OF CLADONIAE 121

G. HAPTERA 122

H. MORPHOLOGY OF THE PODETIUM 122

I. PILOPHORUS AND STEREOCAULON 125

V. STRUCTURES PECULIAR TO LICHENS

1. AERATION STRUCTURES

A. CYPHELLAE AND PSEUDOCYPHELLAE 126
_a._ Historical
_b._ Development of cyphellae
_c._ Pseudocyphellae
_d._ Occurrence and distribution

B. BREATHING-PORES 129
_a._ Definite breathing-pores
_b._ Other openings in the thallus

C. GENERAL AERATION OF THE THALLUS 132

2. CEPHALODIA

A. HISTORICAL AND DESCRIPTIVE 133

B. CLASSIFICATION 135
I. CEPHALODIA VERA
II. PSEUDOCEPHALODIA

C. ALGAE THAT FORM CEPHALODIA 136

D. DEVELOPMENT OF CEPHALODIA 137
_a._ Ectotrophic
_b._ Endotrophic
_c._ Pseudocephalodia

E. AUTOSYMBIOTIC CEPHALODIA 140

3. SOREDIA

A. STRUCTURE AND ORIGIN OF SOREDIA 141
_a._ Scattered soredia
_b._ Isidial soredia
_c._ Soredia as buds

B. SORALIA 144
_a._ Form and occurrence of soralia
_b._ Position of soraliferous lobes
_c._ Deep-seated soralia

C. DISPERSAL AND GERMINATION OF SOREDIA 147

D. EVOLUTION OF SOREDIA 148

4. ISIDIA

A. FORM AND STRUCTURE OF ISIDIA 149

B. ORIGIN AND FUNCTION OF ISIDIA 151

VI. HYMENOLICHENS

A. AFFINITY WITH OTHER PLANTS 152

B. STRUCTURE OF THALLUS 153

C. SPORIFEROUS TISSUES 154