5 66 STUDIES IN FOSSIL BOTANY 



structure of the xylem in the bundles of Bennettiteae 

 still needs further investigation. Beyond the wood 

 is the phloem, often fairly preserved, and the outer 

 edge of the bundle is occupied by a group of bast- 

 fibres. 



The parenchymatous tissue, both of the stem and 

 leaf-bases, abounds in large gum-canals, the contents 

 of which have often become fossilised. These organs 

 closely resemble the similar secretory passages in recent 

 Cycads. 



Between the leaf-bases, and around the fructifications 

 and their bracts, the spaces are densely packed with 

 multicellular hairs, very different from anything known 

 in Cycadaceae, but closely resembling the ramenta of 

 Ferns. The hairs are scale-like structures, one cell 

 thick near the margin, but reaching a thickness of from 

 two to five cells in their middle part (see Fig. 203, B). 

 The cells of which they are composed attain a great 

 length in the longitudinal direction of the ramentum. 

 The ramenta are borne both on the leaf-bases and on 

 the bracts, which, as we shall see, envelop the fructi- 

 fication. The Fern -like character presented by the 

 ramenta is a surprising feature in a genus so far 

 advanced in Phanerogamic organisation as Bennettites. 



We now come to the consideration of the fructifica- 

 tions themselves, and in approaching this subject we 

 must divest our minds of all preconceptions drawn from 

 a knowledge of existing Cycadean cones. The repro- 

 ductive organs of the Bennettiteae are wholly different 

 in organisation, both from the cones which characterise 

 the majority of recent Cycadaceae, and from the rosette 



