B4 liOYAL SUCIITY OK CANADA 



to |ilantK witli an Arawfiirian type of structure, while Dawson in Can.'ula, 

 lnul shown it to he likewise a IVature of the genus Dadoxylon, and 

 this led the way for (fraud Kiii'y to estaljlish the real connection be- 

 tween this genus and Coixlaites; and thiis we have come to employ this 

 last name for those woods with an undoid)trd Ai^uieariau struetuiv, 

 which have hwii slmwii to he related to the leaves and fruits for which 

 tJio name was lirst employed. l{angiug from the Devonian through 

 the l'pi)er Pala'ozoic, into the Misozoie and Tertiary, there tire many 

 plants known thi-ough their wood, which present many points of simi- 

 larity to — 'We may indeed sjiy of airinity with — the Arau<arian type, 

 hut there are many (■oiisidei^itioiis which lead to hesitancy in regarding 

 them as generically idcnticaJ, and among these we may consider the 

 distribution in point of geological time, 'i'hus while Corilaitea' range 

 from the Devonian ujiwards into the Mesozoic, jdants with la. well de- 

 fined Araucarian habit of growth and fructiiication, range from the 

 Tertiary down as far as the Jiifj^Nsic. l)elow which they are unknown. 

 In the Palax)zoic also, tJiere are a niunber of ]>lants known by their 

 wood only, the exact relations of which are matters of doid)t — they can- 

 not be referred to Cordaites m- with certainty to any other known genus. 

 Kraus^ has endeavoured to solve the difTiculty by referring all such to 

 the genera (Vxlro.xylon, Cupressoxylon, Pityoxylon, Araucarioxylon, 

 Pissadendron and Protopitys, and there are structural grounds for the 

 retention of certain elements of this claj^siiication, while admitting the 

 general dasirability of the jtrinciple of conden^ition. On the other 

 hand, Felix and others working on the lines of the present acknow- 

 ledged position of Cordaites, and having reference to the geological dis- 

 tribution of tliese varioiis plants, have suggested the propriety of con- 

 fining the Cordaitea> to Pahvozoic time, while Araucarioxylon is reserved 

 for ^lesozoic and Tertiary times. Under this ruling Dadoxylon be- 

 comes a provisional name reserved for all those fonns which have no 

 recognised alTinity. This idea has been recognised and ntilise<1 by 

 Knowlion,- and although there are obvious objections to it. it may 

 nevortheless l)e regarded as a good provisional basis for further studies. 

 It certainly has the merit of giving a definite line of demarcation be- 

 tween recent types and those of more ancient date, when mere struc- 

 tural resemblances would tend to identify the two. It will also do 

 much toward reducing that endless ivmfusion which comcf^ from a 

 useless midtiplication of names for jilants which, if not generically 

 identical, are nevertheless closely allietl, and as Knowdton very well 



' Schimper's Pal. Veg., II., 1874, 369. 

 » Proc. U. S. Nat. Mus., 1890, XII., 601. 



