136 BENNETTITES. 



leaf-trace as described by Carruthers, and the analogy which 

 he noted between the trellis-work form of the vascular cylinder 

 and the bundle system of a fern stem are confirmed by Solrns ; 

 he adds, however, that a "closer examination will doubtless 

 disclose a greater affinity with the course of the vascular 

 bundles in many Coniferce." 1 The pith and cortex are traversed 

 by numerous and large gum-canals, and the stems are enclosed 

 in the armour of leaf bases characteristic of recent cycads. 

 Between the petioles of Bennettites and those of living cycads 

 there is the closest agreement ; the bases of the leaves are 

 separated from one another by a felt of ramenta-like outgrowths 

 from the petiole surface. Occasionally the substance of the petiole 

 has rotted away, leaving deep cavities occupying the meshes in 

 a network of intervening projecting ridges. In Bennettites 

 Gibsonianus the structure of the lateral branches bearing the 

 remarkable form of fructification is very perfectly preserved, 

 and it is evident that we have to deal with a plant differing 

 in many important respects from the present types of cycads. 

 Referring to the cycadean character of the stem and leaf-stalk 

 of Bennettites, Solms remarks: "We arrive at the surprising 

 result that all the Jurassic and Neocomian stems which are 

 termed Ct/cas-stews, so far as anything is known of their 

 structure, belong to Sennettitece, and that not a single one of 

 them has been proved to be a genuine stem of Cy cadets. This 

 further shows how precarious is the identification of fossil remains 

 when it rests on superficial characters only." The form of the 

 lateral fructification branches may be summarized as follows : 

 They occasionally arise exactly over a leaf base, but in some 

 cases have been pushed somewhat to the side ; as a rule it 

 appears impossible to "determine the precise relative position 

 of the two kinds of organs." 3 The flower-bearing shoots are, 

 at all events, not terminal structures, as in recent cycads. Each 

 fertile branch is made up of several short internodes, and bears 

 spirally-arranged lanceolate acuminate bracts ; in structure the 

 bracts agree for the most part with the larger leaf bases of the 



1 Solms-Laubach (2), p. 422. 



2 Ibid. p. 424. 

 s p. 431. 



