CYCADACEJE. 



CordaitecR. Unger's genus Cordaites, 1 with its large parallel 

 veined leaves and tall woody stem, affords another example of 

 the occurrence of cycadean structures in association with 

 anatomical features suggestive of another set of plants ; in this 

 case it is with the Coniferce that cycadean characters appear to 

 be combined. In the Mesozoic floras we have Carruthers' genus 

 Bennettites, to which reference has already been made, with its 

 combination of cycadean and coniferous characters. Another 

 and less accurately known plant, Williamson! a,- offers a difficult 

 problem to the palaaobotanist ; but here, again, we have probably 

 to deal with a synthetic type closely allied to Bennettites. 



Enough has been said to show the promising character of 

 the study of the geological history of cycads, and we may not 

 unreasonably entertain the hope, that we are within a measurable 

 distance of deciphering some of the earlier chapters in the records 

 of cycadean development. 



Before considering the questions of terminology and the details 

 of generic and specific determination of fossil cycadean fronds, we 

 may briefly pass in review the recorded facts as to the past history 

 of the CycadacecB, and especially such as have reference to the 

 representatives of this order in Palaeozoic times. In 1868 

 Carruthers 3 expressed the opinion that "no satisfactory evidence 

 exists of the occurrence of Ci/cadeee in any Palaeozoic formation." 

 It is true that the facts we at present possess do not allow us 

 to affirm that the Paleozoic strata contain examples of plants 

 which exhibit typical cycadean structure, and of such a kind as 

 to warrant their inclusion in the Cycadacea as at present defined. 



It has already been shown that certain typical features of cycad 

 structure are met with in various Permo-Carboniferous genera, 

 but these are associated with other morphological characters 

 which are unknown among recent representatives of this class 

 of gymnosperms. It would, indeed, be a matter of surprise if 

 we found in Paleozoic strata a perfectly typical cycadean genus. 

 In the case of Jurassic plants we speak unhesitatingly of cycad 

 leaves, although we cannot as a rule support such assertions with 

 facts of anatomical details or floral structure If external resem- 



1 Renault (1), p. 323. 



2 See Bennettites. 



3 (1), p. 676. 



