﻿DESCRIPTION OF PLATES.* 



Frontispiece. — Longitudinal and transverse sections of bisporangiate strobili and ovu- 

 late cones of Cycadeoidca in natural size and (approximate) color. 



Photographs I and 4, C. dacotensis; photograph 2, C. dacotensis (?) ; photograph 3. 

 C. Wielandi. No. 1 is from a longitudinal section of a bisporangiate strobilus belonging to 

 the collection of the State University of Iowa. No. 2 is from the longitudinal section 

 through an ovulate strobilus numbered 353 in the Yale Museum Cycad Section List. No. 3 

 is the transverse section 393 of two adjacent ovulate cones, and No. 4 the transverse section 

 481 of a bisporangiate strobilus. 



Plate I. Cycadeoidea ingens (type). X 0.25. 



The type specimen, No. 100 of the Yale collection. From locality at southern end of 

 the Cycad Valley in the eastern "Rim" of the Black Hills, shown in photograph 2, plate 

 xlix. This magnificent cycadean trunk is preserved as a huge block of light-gray silica, 

 somewhat elliptical in transverse section, and weighing 304 kilograms (671 pounds). At 

 the summit, as marked by the horizontal arrow on the left of the photograph, the bisporan- 

 giate flower bud illustrated in the succeeding plates 11 and m appears as seen in its original 

 natural position before removal for sectioning. To the right other lines (six in number) 

 indicate the position of the peduncles, p, p, of still other floral axes, synangia being present 

 in one instance, s. Of floral axes as marked by basal portions of peduncles there were 

 originally fully thirty in all, mostly borne by upper two-thirds of trunk and belonging to a 

 single or at most several seasons of flower-producing activity, just preceding the first event 

 in fossilization of parent trunk. Only a few of the axes yet bear basal portions of the fertile 

 staminate fronds as at s; most are simply terminal portions of peduncles surrounded by basal 

 parts of bracts, thus indicating that the strobili of C. ingens mostly protruded farther 

 beyond the armor of immense leaf bases than in the case of the much more lightly armored 

 C. dacotensis, and also making probable such an expansion of the flower bud at the time of 

 pollen maturity as is indicated in the restoration shown in figure facing Chapter VI. 



At the summit of the trunk between the projecting strobilus on the left and the 

 peduncle ends marked by the lines p p on the right, there is a crown of wonderfully pre- 

 served young fronds deeply embedded in ramentum. Several are partly emergent, while 

 others are smaller and completely immersed in the silky ramental mass. Photographs 1-3, 

 plate xix, show the transverse sections of several of these prefoliate fronds. 



Plate II. Cycadeoidea ingens (type). Summit of trunk. X 0.3. 



S (above). — The bisporangiate strobilus denoted by arrow in plate 1 and shown in 

 longitudinal and transverse section in plates in and iv. The slightly worn outer surfaces of 

 the middle portions of the incurved rachides of the yet folded flower or strobilus appear 

 as a more or less regular series of sectors forming a circle, the center of which lies one 

 centimeter above the apex of the inclosed interior cavity marking in part the central ovulate 

 cone as explained in the legend of the following plate. 



S' (below). — A second strobilus, in which a few of the lowermost synangia-bearing 

 pinnules were found to be yet present, most having been broken away during erosion. 



p, p, the peduncles of the other strobili, doubtless similar to those shown at S S'. 



/, position of the helicoid of preserved young and partially emergent fronds illustrated 

 on plate xix. 



* The section numbers throughout the plate legeuds, as in the text, are those of Yale University Museum 

 Cycad Section List, whether so specified or not. These numbers are the oues giveu by the author, and all the 

 fossil cycad sections on which this volume is based were made by him, save the single Lignier section, pho- 

 tograph 3, plate xxviii. Most of the photographs and photomicrographs, as well as various text-figures and 

 the origiual tracings, are also by the author. The ink work on most figures, and the brush drawings, are by 

 the scientific illustrator, Mr. G. S. Barkentin, of Albany, N. Y. 



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