RESEARCHES ON THE CARBON I EE ROUS ELORA. 261 



now be considered as fairly well established. This is not 

 the case with the family of the Sphenophylleai, which we 

 will take next in our survey of Williamson's work. This 

 group is entirely unrepresented in the recent Flora, and 

 its existence has only been revealed by pala^ontological 

 research. 



Our knowledge of these remarkable plants is chiefly due 

 to two men — Renault and Williamson. 



In the fifth memoir of the Phil. Trans. Series (1873) 

 the latter author gave an admirable account of the structure 

 of two species of Sphenophyllum, which he at that time 

 described under the name of Aster op kyllites. The form of 

 the leaves in Williamson's Oldham specimens did not 

 agree with the definition of the genus Sphenopliyllum as 

 then understood. We now know that the foliar characters 

 have a very wide range of variation in Sphenophyllum, and 

 Williamson's specimens are now placed without hesitation 

 in that genus. In memoir v. all the main features of the 

 anatomy were already described ; the secondary growth 

 was at once rightly interpreted by Williamson, though 

 its recognition as such was long evaded by his French 

 fellow- worker, in consequence of the invincible prejudice 

 entertained by Brongniart's pupil against the possibility 

 of cambial growth in a Cryptogam. 



As to one of the two species investigated by Williamson 

 (thatnow known as S. plurifoliatum)t\\&reWa.s never been any 

 doubt. Theother, however (5*. ///^//£'),includessome unusually 

 large specimens, with a very root-like transverse section, 

 and showing some slight differences from the typical forms. 

 Several of the chief authorities, such as Renault, Schenk, and 

 Solms-Laubach, refused to recognise these larger specimens 

 as Sphenophyllum or anything ol the kind, and supposed 

 them to be roots of some unknown plant. It turns out, 

 however, that Williamson was perfectly right. The dis- 

 covery of Sphenophyllum leaves on specimens manifestly 

 identical with the disputed forms has settled the question, 

 and the most formidable of the former opponents, Solms- 

 Laubach, has now announced his conversion to William- 

 son's opinion (45, p. 247). The correctness of our author's 



