﻿274 AMERICAN FOSSIL CVCADS. 



all the outer receptacle and the bracts, ends abruptly where a layer of periderm ( ?) marks 

 the abscission of the annulus (j). The entire cone is shown in longitudinal section on plate 

 xxiv, photograph 2, both basal sides of the section presenting at s identically the same struct- 

 ure and features of preservation. It is hence quite evident that some time previous to 

 fossilization the present axis bore an hypogynous disk which had performed its function 

 and wilted away, leaving behind a small basal portion, subsequently excised by a layer of 

 periderm and left hanging loosely round the stem of the ovulate cone as an annulus held 

 in place by the surrounding bracts. The appearance of the scalariform ground tissue 

 beneath the annulus, as well as that of all the periphery of the upper end of the peduncle, 

 the receptacle, and the bract bases, were the coloration more favorable and the enlargement 

 half again as great, would be much the same as in the similar and homologous ground 

 tissue on the under side of the bracts shown in photograph 3. [These features appear in 

 the present illustrations, if studied under a hand lens.] 



Photomicrograph 2—Cycadeoidea Paynei (T. 272). S. 387. X 3°- Vertical longitu- 

 dinal section through bract from point opposite the apex of the seed-bearing cone, which is 

 shown entire in the longitudinal section, plate xxiv, photograph 6. The upper side of the 

 photograph is that next the cone. Ground tissue with scalariform marking throughout. 

 (Cf. diagrammatic text-figure 60 B.) 



Photomicrograph 4.— C. dacotcnsis (T. 214). S. no. X 200. Portion of a section 

 cutting a synangium longitudinally so as to traverse opposite walls of a sporangial loculus 

 with pollen grains clinging to them. In one of these pollen grains cell structures are cer- 

 tainly indicated. In this view five cells are seen and they appear to be all that were present. 

 In the section itself the walls are distinct, and in the photograph only the superior end of 

 the grain was retouched, so as to complete its outline a little more clearly. Whatever may 

 lie said cf the uncertainty of spore markings in general it is believed that these are not 

 accidental and that they indicate a five-celled pollinial stage. (See page 160.) 



Photomicrograph 5— C. dacotcnsis (T. 214). S. 103. X about 80. Transverse section 

 through the outer layer of palisaded cells enveloping a synangium homologously to the 

 outer palisaded layer of the megaspore. 



Photograph 6.— C. ingens (type) (T. 100). S. 170. X 4- Transverse section through a 

 young frond, cutting folded pinnules and rachis. Belongs to the series shown on plate xix. 



Photomicrograph 7.— The same as photograph 6, enlarged to show summits of ramental 

 scales splitting or fraying up into one-celled fibers enveloping the yojng leaves. 



Plate XXXII. Cycadcoidca dacotcnsis (?). T. 505. S. 353. X 4- 



Longitudinal section through ovulate strobilus. The summit of this beautiful fructifi- 

 cation rises to the same level as the leaf bases of the surrounding armor. The form of 

 the receptacle is abruptly conical instead of rounded as in B. Gibsonianus, B. Morierei, etc., 

 or elongate-conical, as in fruits like that shown on the following plate. For a pen drawing 

 of the present and other strobili borne on T. 505 see text-figures 28 and 66. The former 

 is a tracing from the polished cylindrical trunk fragment, bearing additional fruits to the 

 present, which was seated a short distance outside the area polished. Still more important 

 to a clear idea of the features of the present cone is photograph 5, plate xliii, showing the 

 naturally eroded nearly median section left by the splitting away of nearly all the seed 

 pedicels and scales from all of the side of the conical receptacle. 



Plate XXXIII. Cycadcoidea Marshiana. Trunk and Serial Sections 

 from Ovulate Strobilus. 



Photograph 1. — S. 404. Natural size. Radial longitudinal section of cycadeoidean 

 trunk No. 229, cutting the ovulate strobilus pointed out by the arrow in photograph 2, in 

 an approximately median vertical plane. The arrow in photograph 1 indicates the superior 

 side of the fruit, and the lines a-d the respective serial transverse sections shown in photo- 

 graphs la-id. (ic and id are in reverse position.) {Cf. figure 67.) 



Photographs la-id. — All natural size except la, which is enlarged twice. Serial trans- 

 verse sections cut at successively lower levels from strobilus shown in photograph I, in 



