118 



FOSSIL PLANTS. 



there is required to be known an example of a Dicotyledonous tree having young 

 branches without any radically arranged hgneous tissue. 



" Sigillaria ele(/ans possesses in its anatomy a pecuKarity of considerable interest in 

 a physiological point of view. It is furnished with a medullary sheath, which, there is a 

 strong reason to believe, existed to a certain degree independently of the ligneous 

 zone. But whatever doubt might stand in the way of such a peculiarity possessing 

 itself of our own conviction, so far as Sif/iUaria is concerned, it is clearly demonstrated 

 by what is observable in Lepidodendron and Anabathra, inasmuch as in the former the 

 vascular cylinder has performed its function without the presence of the ligneous zone of 

 the latter ; add to this, that in Anabathra, although these two parts are in immediate 

 contact with each other, the differences which have been pointed out in their respective 

 tissues further prove that they represent independent systems. It will now be seen on 

 what grounds the distinction has been made in this paper between the vascular and the 

 ligneous part of the fossils which have been mentioned." 



11. BiNNEY^ (Roots). — Description of the Dukinfield Sigillaria with long Stigmaria 

 roots, showing how the latter change their characters as they extend outwards from the tree. 



12. Brown" (Roots.) — In a paper on a group of fossil trees, in the Sydney Coal- 

 field of Cape Breton, with Stigmaria roots. 



13. BiNNEY^ (Roots). — Description of Sigillaria reniformis having Stigmaria Jicoides 

 as its roots, from the Pemberton Hill Cutting, on the Bolton and Liverpool Railway. 



14. Hooker* (Roots). — Dr. Hooker describes Stigmaria with close wedges in the 

 woody cylinder, as well as one with open wedges, and shows that these two different roots 

 belong to specimens having the same external characters. He also notices the depth of 

 the bell-shaped cavities from which the rootlets proceed. 



15. Brown^ (Roots). — Description of an upright Lepidodendron with Stigmaria 

 roots in the Sydney Main Coal, in the Island of Cape Breton. 



16. Brown* (Roots). — Description of a Sigillaria, with conical tap-roots found in 

 the Sydney Main Coal. 



17. Brongniart''' classes under Dicotyledones ggmnospermes the family Sigillariees, 

 containing the genera Sigillaria, Stigmaria, Syringodendron, Diploxglon, Ancistro- 

 p/tgllum ? and Bidimophyllum ? and considers that Witham's Anabathra and Corda's 

 Diploxylon belong to the same genus. The same author, in treating on the Dij)loxylon 

 of Corda, writes " Ce genre n'est connu que par sa structure interne, qui me parait se 

 rapprocher du Sigillaria, dont il differe cependant par le cylindre continu, forme par 



1 'Quarterly Journal Geol. Soc.,' vol. ii, p. 391, 1846. 



2 Ibid., p. 393, 1846. 



3 'Phil. Mag.,' s. 3, vol. xxvii, p. 259, 1847. 



* ' Memoirs of the Geological Survey,' vol. ii, part ii, p. 431, &c., 1848. 



5 ' Quarterly Journal Geol. Soc.,' vol. iv, p. 46, 1848. ^ Ibid., vol. v, p. 354, 1849. 



7 ' Tableau de Vegetaux fossiles,' p. 97, 1849. (Ext. Die. univ. d'Hist. Nat.) 



8 Ibid., p. 57. 



