Sk'tion IV., 1900 [ Bl 1 Trans. U. S. G. 



III. — iN'bft.'.i on the North Amrricnn Speries of Dado.ri/lm). vith Special 

 Reference to Type Material in the CollecHons of ike I'eler lied- 

 palh Museum, McGill College. 



By ritOFIiSSOH D. r. 1'EN HALLOW. 



(Read May 29th, 1900.) 



One or two years l)efore his death, the late Sir William Dawson 

 placed in my luiuds a large anioimt of material representing the various 

 species of J)adoxylon collected by him during a i)eriod of nearly half a 

 century, one typical S2)ecies from Eur()[)e, and several supposed species of 

 Cordaioxylon, Tylodendron and Cordaio-Sigillariia, with the request that 

 1 should revise the wliole in the light of our most recent knowledge 

 respecting this most interesting group of plants. In the interval, con- 

 siderable material has come to hand through Trof. C. S. Prosser, from 

 the Permian and Cretaceous of Kansas, and tiiis has been incorporated 

 in the revision, as it was found to embrace severiU well known fonus of 

 Dadoxyion, together with other interesting types. 



Several considerations combined to <i"ive weight to the idea that a 

 revision was not only desiiul)le t nifessary. The /ronus Dadoxyion 

 has been known under a variety (jf names since Witiiam's ])ublication 

 in 1833.' it ha.s been investigated by all the leading paUeol)i)liiiiists 

 of Europe and America since that time, and the abundiince of material 

 in America, but more ixirticularly in France, where it^ remains are to 

 be found in great (juantity <and often most be<autifully j>re6eiTCHl, lias 

 led to its being one of the best known genera of fos.sil pkvnts. So 

 lample liaa been tlie mat/criid, and so perfectly lias it been jiresen-ed 

 ini all its parts, tliat we now have a fairly accurate knowledge of its 

 iiuternal structure, as also of its external characteristics including the 

 foliuge and fruit. Notwithstanding all tliis however, an examination 

 of the literav.ure of the subject discloses a remarkable degree of confu- 

 sion as to the plants which properly fall under this genus, their real 

 afRnities with existing fomxs, and their Ihnitations with respect to 

 geological time. This confusion is not only evident in the type 

 material from this piai-t of the world, but it appears in all the writings 

 of various authorities and does not disappear from the most recent 



' The Internal Structure of Vegetable Fossils. 



