﻿278 AMERICAN FOSSIL CYCADS. 



is a highly instructive section ; it first cuts a cortical peduncle trace above, and then passes 

 through a peduncle insertion and various adjacent leaf bases below. (See figure 96.) 



Photograph 3. — S. 490 (axis 11). Median vertical longitudinal section through an ovu- 

 late strobilus and all of its peduncle, a small portion of the outer cortex being visible to 

 the left in the photograph. An hypogynous annulus of wilted tissue, doubtless the basal 

 remnant of a dehiscent disk, appears at base of the ovulate cone. (See figure 99.) 



Photograph 4. — S. 515 (axis vn). Median vertical longitudinal section through a 

 bisporangiate strobilus passing from its summit through the entire length of the peduncle 

 to its insertion on the cortex. The sporophylls appear to have been partially macerated or 

 otherwise broken down before silicification, although the numerous more or less displaced 

 synangia have reached a full size and are well preserved. The central ovulate cone is 

 partially preserved and in normal position. The complete agreement in length and develop- 

 ment of the peduncle of the present and the ovulate forms is especially to be noted. 



s. n., synangia; 0, base of ovulate cone; s, insertion of the partially conserved pollen- 

 bearing disk; /, axillary leaf-base insertion on cortex. (See restoration, figure 71.) 

 [Position of axes VI, VIII and II on trunk appears in figure 94; of VII in figure 14.] 



Plate XL. Cycadcoidca dacotensis. Serial Thin Sections through Ovulate 



Strobilus. 



The fifth axis of fructification drilled from T. 214 in the form of a cylindrical core. 

 X 1.25. (For position on trunk see text-figure 14, p. 47.) 



Photograph 1. — S. 499. Section cut in an exactly radial longitudinal plane of the trunk 

 and passing through the entire length of an ovulate axis and the surrounding armor, as 

 seated on the cortex. In the photograph the summit of the cone is slightly restored, but 

 in the specimen itself very little of the apex is eroded away, so that a slightly more tangen- 

 tial section would have appeared complete. That the section fortunately is, as cut, a very 

 exactly radial and median longitudinal one is testified to by the fact that bracts are cut 

 throughout all of their length preserved on both sides of the peduncle. All the photographs 

 of the present plate are reproduced 1% the natural size, this slight enlargement being 

 deemed a minor matter so far as concerns the ovulate cones, those in the same stage of 

 growth varying greatly in size, and in some trunks — notably in the in-every-way-comparable 

 T. 54 — reaching nearly twice the diameter of the present example. The planes 501-503, 505, 

 506, 508, and 509 are those of the respective transverse sections shown in the photographs 

 2-8. (See text-figure 100.) 



Photographs 2-8.— Serial transverse sections 501-503, 505, 506, 508, and 509, from the 

 same cylindrical core as S. 499 (photograph 1), but from the opposite half. (It would have 

 been better to have made the transverse series from the same half as the longitudinal sec- 

 tion.) The respective planes of the several sections are vertical to the lines numbered in 

 correspondence with the sections in photograph I. The several arrows indicate direction 

 vertical to the trunk. 



The handsomest feature revealed is the basal fluting of the cone due to bract appres- 

 sion (cf. photograph 3), and the most interesting, the hypogynous annulus of wilted tissue 

 (s, s, photograph 4.) The woody cylinder of the barrel-shaped peduncle, in the present 

 instance but little flattened except near the peduncle insertion on the cortex, is distinct, as 

 is likewise the cortical peduncle trace. (Cf. photographs 5 and 6, also 7 and 8.) 



Plate XLI. Cycadcoidca dacotensis. Serial Sections through a Young 



Strobilus. 



The fourth axis drilled from T. 214 in the form of a cylindrical core. An incipient 

 fructification similar and similarly borne to that shown in longitudinal section in photograph 

 I, plate xxxix. For position on trunk see figure 94, iv, and photograph 12, plate vi. 



Photograph 1 — S. 369 (T. 214). Natural size. Radial longitudinal section of trunk 

 passing from the medulla (m) through the xylem (x), cortex (c), and armor, thus cutting 

 an entire lateral axis in its median vertical plane. The entire bundle course from the xylem 



