﻿PRESERVATION AND EXTERNAL CHARACTERS. 



20 



type specimen of ( 'ycadeoidea Wielandi is compressed and elliptical in outline; but 

 the Yale trunks 393, 745, 771, and 797 may be cited as more or less complete speci- 

 mens positively of this same species, which are plainly cylindrical and uncrushed. 

 Of these, No. 393 deserves especial mention as bearing numerous lateral ovulate 

 fructifications of the type agreeing so closely in structure with those of Bennettites 

 < Itdsonmnus, and as being one of the most beautifully preserved cycads ever dis- 

 covered. (Cf. plate xxi.) It must hence be finally concluded that if any of the 

 Cycadeoidese exhibited transverse ellipticity in life, this has been merely occasional 

 or the result of growth as a branch in a restricted or oblique position, and that this 

 character can not be considered as having either generic, specific, or even varietal 

 value. 



Fig. 4. — Tuberous and Low-growing Columnar Cycadean Trunk Types. 

 To the left. — Stangeria paradoxa. A staminate plant bearing two cones. Tuberous, subterranean, nearly 



armorless trunk, with fern-like foliage. About one-twelfth natural size. From Warming. 

 To the right. — Encephalartos Hildebrandtii and E. villosus. A, low columnar armored trunk ; B, cone of 



A; C, ovulate cone (of E. villosus). A. one-sixteenth, and B and C, one-eighth natural size. From 



Engler and Prantl. (Cf. figures 5, 6, etc.) 



TRUNK TYPES. 



The cycadean type of trunk, as described in greater detail in the succeeding and 

 ninth chapters, is a generalized one, characterizing as it does a great plant alliance, 

 which has been abundantly represented since Permian time. Its chief features — a 

 laro-e central pith followed by a thin, woody zone enveloped by a cortical parenchyma 

 traversed more or less regularly by leaf-trace bundles, and an outer armor of leaf 

 bases inserted in spiral order — are seen in the widest variations of structural detail 

 and relative development. In addition there is present in the older forms, as in tree 

 ferns, a more or less abundant ramentum, and, in the more recent forms, series of 

 abortive or scale leaves alternating with the normal foliage leaves. The scale leaves 



