﻿54 



VEGETATIVE FEATURES. 



Fig. 22. — Cycadeoidea turrita. T. 269. 



Transverse section of leaf bases surrounding an isolated lateral 

 strobilar axis bearing two large basal bracts, one of which 

 is cut at and the other a little above the insertion on the 

 peduncle. Tangential to trunk near its base. The leaf 

 base bundle systems are indicated. Note the pair of 

 heavier bundles in the upper leaf base angle. Natural size. 



or else simpler, types of ramenta are present in most existing cycads, as in certain 

 species of Macrozamia and Encephalartos {cf. text fig. 17); and it has been stated 

 that in New South Wales they are, together with the chaffy scales of fern petioles, 

 known as "pulu," and used as a stuffing 

 for cushions. 



The profuse and highly character- 

 istic development of ramentum in the 

 fossil cycads, when contrasted with its 

 very reduced condition in the existing 

 forms, might at first sight lead to the •« 

 opinion that herein is a broad distinction 

 of value in the definition of the separate 

 great groups to which the existing and 

 extinct Cycadales have sometimes been 

 assigned. But such is not the view taken 

 here, the presence or absence of ramentum 

 being regarded as in actuality of scarcely 

 more than generic value. Ramentum is, 

 as noted, very abundantly developed in 

 the Cycadellas, and also in Cycadeoidea 

 dacotensis. But it is nearly absent in 

 such forms as C. Stillwelli&nA. C. excelsa; 

 and were a trunk with some ramentum 

 like that of Dion fouud accompanying 

 either of the above fossils, no one would 

 consider the difference, so far as this 

 feature is concerned, as of more than 

 generic value, or perhaps even — depend- 

 ing upon the temperament of the inves- 

 tigator — of more than specific value. 

 Were all existing cycads without any 

 traces of ramentum, and were all the 

 fossil forms as densely enveloped in ra- 

 mentum as C. dacotensis, the case would 



be more obscure. Plainly, however, the Fig. 23.— Cycadeoidea Wielandi. T. 393. 



intervening Stages between the extremes Oblique tangential section cut from near the base of a trunk 



do exist, and the inference is virtually 

 conclusive that the Cycadeoidese and 

 Cycadacese have been alike subject to a 

 progressive reduction of the profuse 

 ramentum characterizing their common 

 Paleozoic filicinean ancestry. In Meso- 

 zoic time reduction had simply not progressed so far. The causes of this disap- 

 pearance of ramentum, of course, constitute another subject. Since the tree ferns 



bearing numerous ovulate strobili. The section plane 



passes through armor into the cortex. Lowermost leaf 



bases cut I cm. distal to the cortex. 



I. bundle trace of a peduncle ; II and 111, peduncles that may 



represent scattering fructifications borne previously to the main 



series, or else abortive fruits ; IV, a peduncle of one of the finely 



silicined fruits, showing the woody cylinder. To the left of 



fruit axis I are shown heavy bundles of the outer cortex which 



are on the point of splitting up into the leaf base bundles. 



