[.'EM. ALLOW] NORTH AMKHirAX SI'KCIKS OF DADOXYLON 63 



"Les espeees-type do ce geure sont les Dadoxylon J'.raiidlingu ct 

 J)adoxyl(>ii tchiliateholliiijiuin,"' and with respect to tht> fonuer at least, 

 tliJS view has been jreuerally ivco-iiised. It is therefore desirable that 

 the histological characters of tiiis species siiould be imstnl in review in 

 the present connection. 



The niateriul in Jiand was derived from St, Etienne, France, and 

 may therefore bo regarded as typical. Excelleni iigure*5 of this plant, 

 with respect to its interniil structure, have alreudv been given by Zittell, 

 Schimper & Sclienk; by WitJiam tuid also by Uoppert, and willi these 

 our photographic figures iigree. But in the various descriptionii so far 

 given, certain details of importance are not taken into consideralion, 

 and these are now emiwdied in the diagnosis preseuted here. One of the 

 best descriptions of tiie plant as already recorded, is that given by Un"-er 

 to the following effect-: — ° 



" D. ligni strtitis conccntraticis obsoletis, vasis amplis Icptotichis, 

 poris bi-tri-qnadriserialibus contiguis, radiis medullaril)us simplicibui 

 aut rarius compositis e cellulis 1-1? superpositis formatis." Some of 

 these details properly belong to the description of the genus, for which 

 we resen-e them. To the others we add such as may serve to clearlv 

 differentiate this species from the others now under consideration, and 

 tit the same time preserve its typical character. 



Transversc.-Pith cells about 62 mic. b, jad, the wails about 16 mic. thick 

 Tracheids somewhat elongated radially, about lo x 38 mic the walla 

 about 6 mic. thick. 



Iiadial.-Ra.y cells more or less conspicuously contracted at the ends- short 

 equal to about 1-3 tracheids; the pits on the lateral walls oval or 

 round, narrowly or obscurely bordered, 1-3, chiefly 2 per tracheid 



Bordered pits typically hexagonal, in 1-3, chiefly 2 rows through- 

 out the tracheid, and in the region of the protoxylem showing numer- 

 ous and striking transitional forms from scalariform vessels ; 12.5 

 mic. broad. 



The pith shows characteristic Sternbergia structure, the cells 

 flattened vertically. 



Tangent iaI.-R&ys low, narrow, 15.5 mic. broad; the oblong cells 1, or some- 

 times 2-seriate in part. 



• Diet. univ. d'Hlst. nat., 1849, 97. 



• Gen. et Spec. PI. Foss., 1850. 



