﻿290 



AMERICAN FOSSIL CYCADS. 



Cordaites — Continued. 

 Stamens of, 245 

 Silicified strobili of, 176 

 Cordaites Brandlingi, 198 

 Cordaites Newberryi, 75, 76, *y8 

 Cone-axis, structural significance of, 224-226 

 Cortex of — 



Cycadacea, 66, 201-205, 206 



Cycadeoidea, 66-74 

 Corypha umbraculifera, culminant fructification 



of, 126, 128, 185 

 Cyathea, ramentum of, 52, 53 

 Cyathea excelsa, ramentum of, *5i, 53 



medullaris, 195, 239 

 Cycad collections in — 



American Museum of Natural History, 7, 9 



Johns Hopkins University, 4, 5, 6 



State University of Iowa, 7, 39 



State University of Wyoming, to 



United States National Museum, 7, 9, 39 



Woman's College of Baltimore, 6 



Yale University Museum, 8, 10 

 Cycad Valley, 94 

 Cycadacea, 102, 236 



Archegonia of, 219 



Bundle system of seed, 219-221 



Cone-axis, structure and significance of, 224- 

 226 



Cortical bundle distribution (see Trunk struc- 

 ture) 



Distribution of existing genera of, 189 



Embryos of, 226, 234 



Fern-like characters of, 239-240 



Fertilization, role of generative cell in. 216 



Foliage of, 209-213 



Fructification of, 213-226 



Fruits of, 226 



General description of, 189-226 



Leaf development of, 209-210 



Megaspore bundle supply, 222, 224 



Megasporophylls of, 217 



Microsporophylls of, 215 



Monoxylic trunk forms, 196 

 Description of, 197-199 



Northern limits of, 192 



Occidental genera of. 189 



Oriental genera of, 189 



Ovules of, 217-219 



Ovulate cones of, 214, 215 



Pollen of, 216 



Polyxylic trunk forms, 196 

 Description of, 199 



Prefoliation of, 84, 85. 86, 210 



Ramentum, 54 



Rarity of definitely known fossil forms of, 

 190 



Resume of vegetative characters of, 213 



Root of, 207-208 



Seed-bundle system in, 219-221 



Seed integument of, 219 



Simple-stemmed forms, 31 



Size of, limited by stem structure. 35 



Sori of, *2I4, 215, 216 



Cycadacea — Continued. 



Staminate cone, homologies of, 235 

 Summary of relationships with Cycadeoidea, 

 226-235 



(a) Vegetative characters, 227-228 



(b) Reproductive characters, 228-235 



(c) Strobilar homologies, 235 

 Thorny frond growths of, 212 

 Trunk structure of, 195-208 



Armor, 204 

 Cortex. 66, 201-204 

 Medulla. 195-196 

 Periderm. 205-206 

 Vascular zone, 196-200 

 Cycadales. 54. 76, 230, 236, 237, 238, 244 

 Cycadea, 142. 236, 237, 238 



Causes of stature of, 35 



Lateral buds of. 30 



Ovulate cone, homologies of, 235 

 Cycadella, 22. 2S, 31, 77, 100, 101, 166, 210, 227 



Profuse ramentum of, 51 



Size of trunks, 31 



Species of, 10, 11 

 Cycadella ramentosa, 82, 104 



Foliage of, 100-102 



Pinnule structure, 101 



Rachis, 101 



Ramentum, *52 

 Cycadella sp., transverse section of trunk, *66 

 Cycadella (Cycadeoidea) utopiensis, 8, 9 



Leaf bases of, *53, *63 

 Cycadella wyomingensis, strobilus of, 167, [229] 



Young bisporangiate strobilus of, *I75-I76 

 Cycadeoid-angiosperm juxtaposition, 243-246 

 Cycadeoidales, 236 

 Cycadeoidea, 8, *99, 100, 101, *i09, *I55, *i65, 245 



Abundance of cones in certain Black Hills 

 species of, 108 



American localities of, 6-10 



Armor of, 51-56 



Expanded strobili of, *io6, 155, 156, *i64 



General character of foliage, 102-104 



Generic value of, 30, 78 



Localities of the Black Hills types of, 9 



Maryland types of, 6 



Medulla, 77, 78 



Medullar cavities, 77 



Megasporophyll homologies of, 230-233 



Microsporangiate fructification of, 142, 246 



Nuclei of medullar cells, 78 



Phloem, 76 



Ramentum. 51-54 



Seed resemblances of. 234 

 Cycadeoidea sp. 



Distortion of leaf base spirals in, *6o 



Leaf bases, *55, *s6, *57 



Section 389, *i70, 171 



Section through crown of young fronds, *99 



Sections 410 and 411. 169, *I70 



Surface of fruit, *I09 



Young fructifications of, 168-174, 176-186 

 Cycadeoidea Colei, 7, 163 



Young fruit of, 174 



