﻿262 AMERICAN FOSSIL CVCADS. 



Fi.ate V. Cycadcoidca. Typical trunk forms, showing stages of growth 



and fructification. 



Photograph 1. — Cycadeoidca Marshiana. Height, 45 cm. ; weight. 147 kg. Collected 

 by Wieland at Minnekahta, S. Dak. The largest of a group of three branches associated 

 in situ, but no longer organically connected. These trunks rested on a bluish clay stratum 

 overlaid by a sandstone horizon. As found, they were completely embedded, the smaller 

 of the trunks almost entirely in sandstone and the largest one here figured mainly in sand- 

 stone matrix, but forming for itself a slight depression or bed in the underlying clay ("Lie- 

 genden"). These several silicified trunks no doubt belonged to a group that was closely 

 connected in life, and at the time of its fossilization subjected to pressure by an inrush of 

 matrix sand forcing the separate branches somewhat asunder as they lay on a clayey lake 

 bed, or, possibly, estuarine river deposit. (Cf. account of discovery of these trunks given in 

 Chapter II, page 40.) Notwithstanding the great size of the branch figured, it had never 

 produced more than a very few if any fructifications, as quite plainly indicated by the yet 

 strongly marked regularity of the leaf-base spirals, but slightly thrust aside by the emer- 

 gence of the various small and young lateral fructifications when the chain of events that 

 led to fossilization began. This branch was, in short, just then leaving what is explained 

 in Chapter VI as the pulcherrima stage of growth or condition of symmetrical leaf-base 

 spirals preceding rearrangement due to the emergence of large numbers of lateral fructi- 

 fications, and probably marking the closing stage in the life of many of the Cycadeoidepe. 



Photograph 2. — Cycadcoidca dacotensis (T. 54). Height, 43.5 cm.; weight, 96.6 kg. 

 Stage of growth, in which the spiral order of the leaf bases has been obscured over all the 

 lateral surface of the trunk by the emergence of large and numerous strobili. While this 

 is unquestionably an example of culminant fructification, the strobili are not all in exactly 

 the same stage of development. Some of those present are in the bisporangiate condition, 

 and pollen fills the loculi in the synangia borne by the yet folded or prefoliate staminate 

 disks. In other cases the disks (so far as originally present) have been shed and the ovu- 

 late strobili, though not yet matured, are of larger size, fully 5 cm. in diameter. One of 

 these (O. S.) is indicated, all the bract tips and apical portion of the seed stem and inter- 

 seminal scale region having split away so as to expose the summit of the large receptacle, 

 as plainly appears in the photograph. 



Photograph 3. — Cycadcoidca Marshiana. X 0.17. A Minnekahta, South Dakota, speci- 

 men in a stage of fruit growth somewhat intermediate to the two preceding. (Originally 

 received as three fragments, subsequently found to join as an entire trunk.) 



Photograph 4. — Cycadcoidca rhomhica. A characteristic species of simple-stemmed 

 tnrik in the pulcherrima stage. X 0.33. From the Piedmont-Black Hawk region of South 

 Dakota. Only a few small and as yet young and indistinct fructifications are present. Had 

 the trunk been fossilized a few years sooner no fruits would have been evident and the 

 spiral succession of the leaf bases would in consequence have been an uninterruptedly 

 symmetric one. 



Photograph 5. — Cycadcoidca turrita (T. 76 + 375). A medium-sized columnar speci- 

 men remarkable for the regularity of its leaf-base spirals, which are undistorted, save for 

 the emergence of the single ovulate strobilus (O. S.) shown in median longitudinal section, 

 photograph 1, plate XXV. 



Plate VI. Group of low-growing Cycadeoidcan trunks, both simple-stemmed 

 and branched, from the Lower Cretaceous (or Uppermost Turassic?) strata 

 of the Black Hills Rim. 



Illustrating various habits of growth, stages of fructification, and types of preserva- 

 tion, shown by specimens in the Yale collection figured by Wieland in the Yale Scientific 

 Monthly for March, 1900. The photographs are about one-ninth natural size. (Catalogue 

 numbers in parenthesis.) 



