《American fossil cycades》求取 ⇩

INTRODUCTORY3

CHAPTER Ⅰ.—DISCOVERIES AND COLLECTIONS5

American localities and types5

Maryland5

Isolated or little known localities6

Discovery of cycads in the Black Hills7

Cycad localities of central Wyoming10

California10

Occurrence and distribution of North American fossil cycads in time11

European cycads, discovery of various historic types12

Cycads of India16

Old World Types of Cycadeoide?, the horizons in which they occur, and the museums in which they are located18

CHAPTER Ⅱ.—PRESERVATION AND EXTERNAL CHARACTERS21

Varying conditions of fossilization and resulting trunk forms21

Local conditions of preservation23

Rare occurrence of conditions requisite for mineralization of cycadean trunks26

Trunk forms due to compression during or after fossilization26

Trunk types29

Low growing unbranched trunks31

Short columnar trunks33

Columnar trunks distinctly more than one meter high33

Branching trunks36

Résumé44

CHAPTER Ⅲ.—ON THE METHODS OP SECTION CUTTING45

VEGETATIVE FEATURES49

CHAPTER Ⅳ.—TRUNK STRUCTURE51

Armor51

Ramentum51

Leaf bases55

Outer features and arrangement55

Leaf-base bundle grouping59

Leaf-base bundle structure64

Cortex66

General features66

Cortex of trunk39368

Xylem zone74

Phloem76

Medulla77

Cycadeoidea Jenneyana and C.ingens78

CHAPTER Ⅴ.—FOLIAGE81

Historical81

Foliage of Cycadeoidea ingens (type)83

Prefoliation86

Form and structure of fronds and pinnules87

Preservation of microscopic features91

Comparison with existing cycads93

On Yale cycad No.208 (a cotype of Cycadeoidea ingens) and its adventitious leaves94

Cycadeoidea colossalis (trunk133)98

Cycadeoidea colossalis (trunks 2 and 10)99

Cycadella ramentosa100

Remarks on general characters of cycadeoidean foliage100

REPRODUCTIVE STRUCTURES105

CHAPTER Ⅵ.—OVULATE CONES107

Historical107

Ovulate cone of Cycadeoidea Wielandi108

General features109

Peduncle and its bundle supply113

Evidence of presence of hypogynous disks114

Bracts115

Interseminal scales116

Seed pedicels118

Seeds120

Embryos and pre-embryonal structures124

Cone-bearing habitus of various trunks126

Bisexuality130

Cycadeoidea Jenneyana (?)131

Cycadeoidea dacotensis (?)133

Cycadeoidea Marshiana135

Résumé137

CHAPTER Ⅶ.—BISPORANGIATE AXES139

Historical139

Organization of the bisporangiate strobilus of the Cycadeoide? (Materials)143

Cycadeoidea dacotensis144

Peduncle146

Bracts146

Ovulate cone147

Staminate disk149

Expanded strobili155

Histological details157

Synangia158

Pollen grains159

Cycadeoidea heliochorea162

Cycadeoidea ingens and C.Jenneyana162

Cycadeoidea Paynei163

Résumé165

CHAPTER Ⅷ.—YOUNG FRUCTIFICATIONS169

Cycadeoidea sp.(sections 410 and 411)169

Cycadeoidea sp.(section 389)170

Cycadeoidea pulcherrima (？)(section 409)171

Cycadeoidea superba (type)171

Cycadeoidea Paynei(?)174

Cycadeoidea Colei (?)174

Cycadella Wyomingensis175

The young ovulate axes of Cycadeoidea dacotensis176

Fruits Ⅸ, Ⅵand Ⅷ177

Fruits Ⅰand Ⅲ180

Fruit Ⅶ180

Fruit Ⅹ180

Fruit ⅩⅣ181

Fruit Ⅱ182

Fruit Ⅴ183

Bisexuality of Cycadeoidea dacotensis184

Fruiting habit of Cycadeoidea dacotensis184

The pulcherrima stage of trunk growth186

RELATIONSHIPS187

CHAPTER Ⅸ.—EXISTING AND FOSSIL CYCADS COMPARED189

The Cycadace?189

Distribution189

Zamia191

Zamia floridana192

Trunk structure195

The medulla or pith195

The vascular zone196

The cortex201

The armor205

The periderm205

The root207

The leaves209

Résumé of vegetative characters of the Cycadace?213

Fructification213

Microsporophylls215

Fertilization216

Megasporophylls217

Ovules217

Bundle system of seed219

Structure of megaspore bundle supply222

Structure and significance of the axis of the cones224

Fruits226

Summary of relationships of the cycadeoidean to existing Cycads226

Comparison of vegetative characters227

Comparison of reproductive characters228

Tabular comparison of ovulate and staminate cones235

Systematic position of the Cycadeoide?236

CHAPTER Ⅹ.—FERN ANCESTRY AND ANGIOSPERM ANALOGIES239

The fern cycad relation summarized239

Sporophyte reduction correlated with elimination of separate pro-thallial stages and evolution of seed-bearing quasi-ferns241

Ultra-relationship of the cycadalean gymnosperms (or the cycadeoid angiosperm juxtaposition)243

BIBLIOGRAPHY249

EXPLANATION OF PLATES259

LIST OF TEXT FIGURES285

INDEX289

ADDENDA ET CORRIGENDA296