524 STUDIES IN FOSSIL BOTANY 



this kind still enclosed in wood, which proved on 

 investigation to have the structure of Araucarioxylon. 

 This was one of the first steps made towards the 

 reconstruction of these fossils, for we now know that 

 the wood in question, resembling that of the recent 

 Araucarias, belonged to certain members of the 

 Cordaiteae. The peculiar appearance of the casts, as 

 Williamson explained, is due to the discoid structure 

 of the pith, such as is found, not only in the Walnut, 

 and in some Jasmineae and Euphorbiaceae, but also 

 in certain species of Pinus, at the present day. The 

 pith undergoes transverse rupture in many places, so 

 as to leave numerous diaphragms, separated by empty 

 spaces. The constrictions on the cast in the fossil 

 specimens, mark the position of the diaphragms (cf. 

 Fig. 190, A). 



The recognition of the true nature of Sternbergia 

 has proved important, for by this means the large, 

 rooted stumps, found in the Coal-measures of the 

 Loire, containing Sternbergia casts, have been identified 

 as belonging to Cordaiteae. 



The floral organs of the Cordaiteae were known, so 

 far as thek- external characters are concerned, long 

 before their nature was recognised. These fossils, 

 which were at first placed in the provisional genus 

 Antholithus, consist of a simple or branched stalk, 

 bearing laterally little catkin -like bodies, not often 

 exceeding a centimetre or so in length. The male 

 and female catkins cannot always be distinguished 

 externally ; in some forms, however, the axis of the 

 female inflorescence appears to have borne solitary 

 ovules, accompanied only by a few bracts. 



