[i-KM!.M.i.n\v] NOHTII AMKIMC'AN Sl'KCIKS OF DADOXYLON B8 



has now been broug-ht to a conehision, it is to be regretted that circiun- 

 suvnces so delayed it as to prevent mu from completing it (hiring the 

 life-time of Sir William Dawson, and tliivroby roceiving the co-operation 

 and advice of one who ha'' so closely identified himself with these plants. 



In the oonrse of my work T liave endeavoured to take a complete 

 survey of the literature of the subject. This luus not been jwssible in 

 the fullest sense, since one or two of the more important works have not 

 been accessible. In nearly (all cases, however, statements have been 

 voriiied by direct reference to the original publiaition, and it tlius be- 

 comes possible lo give a more extended and complete l)il)liMgraphy of 

 the genus and of tlie individual species than has previously appeared. 



A det'ailed historical summary in this connection is rendered uu- 

 necessar}' by the presentation given by Knowlton, who clearly states tne 

 historical Itasis on which our present views rest.* But a brief resiun6 

 of the principal phases in our knowledge relating to this interesting 

 group of plants, may sei-\e to bring out somewhat more clearly, the 

 bearings of the present discussion. 



Our knowledge of those plants which have been variously known 

 among others, by the names of Da<loxy',on, Cordaites, C'ordaioxylon, 

 Araucarites, Araucarioxylon commenced in 1833 with a description of 

 several species of Pinites by Witham. In 1847, Endlicher descril>ed 

 fourteen s])ecies of these pUints under the name of Dadoxylon. A re- 

 cognition of the now well known Arauc.arian structure of the stem, 

 led I'resl to adopt the name of Araucarites, which \\iis subsequently 

 changed to Araucarioxylon i)y Kraus and in a restricted sense, is still 

 retained. In 1850, linger aj^liod the name Cordaites to certain leaves 

 from the Pala'ozoic formation, and a few yeai!s later Geinitz was able 

 to bring under the same designation, -vUrioiis parts of plants which had 

 hitherto been assigned to several separate genera, but which he recog- 

 nised as belonging to Cordaites. Grand Eur}''s investigations of the 

 Carboniferous of the Loire, led to most impori:ant results. The great 

 abundance of material which he was able to collect, and the often per- 

 fect state of its preservation, joined to the studies which Brongniart 

 had already made of tlie silicificd seeds from St. Etienne, pennitted 

 him to obtain a most conqdete history of Cordaites. Among otlier im- 

 portant restilts reached, he was able to prove that the Cordaitea* were 

 gymnospennous plants, and that tlie problematical Artisia or Stern- 

 bergia, which had for so long been a puzzle to pala'obotanists, was noth- 

 ing more nor less than the pith of Cordaites. In the meantime, how- 

 ever, Williamson in England had shown that Stembergia pith belonged 



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



