﻿DESCRIPTION OF PLATES. 267 



lower peduncle is cut beneath all its bracts. The present and the preceding sections thus 

 afford a series of three peduncle sections, the lowermost of which passes near the cortex 

 and beneath all the bracts, the middle one through the two laterally-borne basal bracts, 

 and the uppermost through five bracts. (Cf. outline text-figure 31.) 



Photograph 3. — Cycadella sp. A series of leaf bases that would be difficult to orient 

 were the leaf-base bundle patterns not preserved. Old peduncle traces may perchance be 

 present outside the area of this thin section. 



Photograph 4. — Cycadcoidca Wielandi. T. 393. S. 395. Thin section cutting leaf and 

 peduncle bases as well as a very young fruit or latent bract-bearing bud near the base of 

 the armor, and then passing obliquely to the trunk into the cortex above, where a peduncle 

 bundle trace is cut. (Cf. outline text-figure 23.) 



Plate XVIII. Cycadella ramentosa. S. 445. 



Transverse section of a very young frond, cutting through non-emergent rachis and 

 folded pinnules, all deeply immersed in a luxuriant growth of ramentum and borne laterally 

 on the trunk. Enlarged 35 times. The fluted character of the rachis may be due in part to 

 some form of shrinkage or desiccation. The Podozamites-like attachment of the pinnules 

 very near to the midline is indicated. 



Plate XIX. Cycadeoidean Foliage. 



Leaf structure and prefoliation of cycadeoidean trunks, as seen in photographs of 

 transverse thin sections of prefoliate to partly emergent crowns of leaves, and in isolated 

 young leaves borne laterally amongst older leaf bases and photographed in their natural 

 position on the trunk, in both naturally and artificially polished sections. 



Photographs 1-3. — Young leaves from the crown of Cycadeoidea ingens type, from 

 position indicated in plate 11. Enlarged about three times. In photographs 1 and 2 the 

 summit of the rachis may be noted, but in 3 one sees only the pinnules, which rise at least 

 5 cm. above the end of the rachis in this instance and perhaps several centimeters more. 

 (The pinnule ends were eroded away.) Photographs 1 and 2 are from the adjacent thin 

 sections 167 and 168, and 3 is from thin section 169. 



Photograph 4.— Cycadeoidea sp. Portion of transverse section cut about three centi- 

 meters beneath the summit of an isolated bud bearing a prefoliate crown of young leaves 

 deeply embedded in ramentum. Note the heavy V-form of the bundle pattern of the two 

 rachides on the left side of the photograph, a feature more distinctly appearing in drawing of 

 this section, text-figure 52. 



Photograph 5. — Cycadeoidea Marshland. Portion of a transverse section cut similarly 

 to the preceding and showing the profuse growth of ramentum about the apex of the trunk. 

 In this section the young leaves are not preserved, although structure may be present a 

 centimeter or two lower down. The orientation of the ramentum in regular lozenge-shaped 

 areas disposed in helicoid order, indicating the incipient leaves of the terminal bud, is a 

 striking feature, the more so since the present section is cut 5 cm. beneath the summit of 

 the enveloping bud ramentum. 



Photographs 6-8. — Cycadeoidea Jcnncyana (T. 208). Transverse sections of prefoliate 

 young leaves borne laterally on trunk. Enlarged about three times. Nos. 6 and 8 are photo- 

 graphed from sections of partially emergent leaves polished by hand without removal from 

 the trunk, whilst the slightly oblique section shown by photograph 7 was naturally polished 

 on the original specimen by sand-laden winds. (Cf. text-figures 44, 49, and 51.) 



Plate XX. Vascular Bundles of Cycadeoidese and Cycadacese. 



Photographs of transverse sections of vascular bundles from the leaf bases of fossil 

 cycads, together with supplementary figures from existing forms. The latter are from 

 Mettenius (92). 



Photomicrographs 1-4. — Cycadeoidea dacotensis. X 86. All from T. 214. 1, S. 506, 

 2-4, S. 484. Transverse sections from middle region of leaf bases. No. 1 is the lowermost 

 of these sections; compare its large body of centrifugal xylem with that of the quite similarly 

 proportioned lowermost bundle from the leaf base of Dion edule, figure 1. For further 

 explanation see text-figure 34. 



