268 SCIENCE PROGRESS. 



are the roots, and the appendages which they bear, the root- 

 lets. This has been questioned by various authors, who inter- 

 pret the main axis as a rhizome, and the appendages, or at 

 least some of them, as modified leaves. The question is a 

 difficult one, more especially when we consider that in re- 

 cent Lycopods the differentiation between stem and root 

 is scarcely so sharp as in other vascular plants. Although 

 the principal Stigmarian axes differ very widely both in 

 anatomy and morphology from any known roots, yet the 

 resemblance of their appendages to the monarch roots of 

 Isoefcs or Selaginella is certainly very striking, and it is by 

 no means improbable that Williamson's interpretation of 

 their homologies mav turn out to be the right one. 



In the long controversy as to the secondary formation of 

 tissues by means of a cambium in Vascular Cryptogams, 

 Williamson had most English and German pala^obotanists 

 on his side. The brunt of the battle, however, was borne 

 by him, and to him the honours of victory are due. How 

 complete this victory was may be shown by the opinions ex- 

 pressed by two leaders of the French school, both of whom 

 were among his former opponents. Grand 'Eury expresses 

 himself as follows (48, p. 195): " In any case the opinion 

 that the Sigillaricr and Calamodendra are Gymnosperms 

 sees from day to day the number of its adherents diminish. 

 At the end of my studies in Le Gard I have been led to 

 consider them as highly organised Cryptogams." 



Zeiller, in a letter to Williamson, dated 24th March, 1895, 

 says : " I now at last think the question as to placing the 

 ' Calamodendreae ' among the Cryptogams definitely settled. 

 . . . Your work (29) enables me at last to assert without 

 any reserve the Cryptogamic nature of all this group, as 

 regards which I had thought it right until now to mention the 

 opinions of Brongniart and Renault, though strongly opposing 

 them." 



This relates to the Calamaria; ; as regards the Sigillariae 

 Zeiller had convinced himself long before. An interesting 

 incident of the controversy w T hen at its height was the pub- 

 lication by Williamson and Hartog of a controversial memoir 

 on Sigillaria and Lepidodendron, written in the French Ian- 



