Chap, v Palaeobotany , 1860-1900 135 



not show secondary thickening in their structure, and, 

 claiming that secondary thickening was peculiar to the 

 flowering plants, referred the section of the Calamodendreae 

 to the Gymnosperms. His followers accepted this position 

 and extended it to the Lycopodiaceous types as well. 

 Williamson showed by many researches that secondary 

 thickening is only a subordinate character, and that 

 the general affinities of form and structure in the several 

 groups are much too complete for Brongniart's separation 

 to be scientific. His opinions gradually obtained accep- 

 tance, even Renault at last acquiescing in the correctness 

 of his views. 



The position Williamson assumed in England was taken 

 in France by Renault. A pupil and collaborator of Bron- 

 gniart, he succeeded him as the leading authority on 

 palaeobotany on the continent of Europe. It is difficult 

 to say whether he or Williamson exercised more influence 

 on the study of the time. 



Renault was especially known in connexion with the 

 microscopical investigation of the structure of fossil 

 plants — a field which, at the time of his appearance, had 

 not been very greatly cultivated. His work was so exten- 

 sive and ranged over so much ground that it is impossible 

 in the space available to do justice to it. A brief reference 

 to his more important contributions is all that is possible. 

 One of his earliest papers contains his discovery of the 

 anatomical structure of Sphenophyllum, which he com- 

 municated to the French Academy in 1870. In 1874, in 

 collaboration with Grand' Eury, he described the anatomy 

 of a Sigillaria, a fossil which had been discovered in 1839 

 by Brongniart, who then gave the world for the first time 

 an account of a member of this group. In 1875 Renault 

 discovered Botryopteris, and published a description of 

 the internal structure of the stem, the petiole, and the 

 fructification. In the next year he described the fructifica- 



