HITHERTO KNOWN AS STEENBERGI^. 347 



already noticed by M. Brongniart He characterises one 

 of his groups of coniferous woods by " L'uniformite de den- 

 site du tissu, d'oii resulte Tabsence de couches annuelles 

 distinctes, caractere qui appartient surtout a des bois des 

 terrains anciens, 6videmment etrangers aux vrais Pinus 

 dont il n'y a aucune trace dans ces formations." — {Tableaux 

 des Genres de VSgetaux Fosdles^ p. 76.) 



In fig. 6 is represented the aspect of this tissue in a ver- 

 tical section, cut parallel with the medullary rays, which are 

 seen crossing the section at 6 d. The fibres have an aver- 

 age diameter of the -~ of an inch, and even under a low 

 magnifying power their walls are seen to be covered with 

 minute reticulations. On applying an object glass having 

 a magnifying power of about 280 linear, we obtain the 

 beautiful appearance represented by the sketch fig. 7, in 

 which is delineated a small portion of two of these fibres 

 as they appear in the above section. 



The reticulations are obviously caused by the apposition 

 of alternating rows of the disks characterising coniferous 

 pleurenchyma. The language which M. Brongniart em- 

 ploys in describing the genus Dadoxylon is strictly appli- 

 cable to them: ' Ces especes ont, en effet, la plupart des 

 caracteres esaentiels du bois des Araucaria, c'est-a-dire les 

 ponctuations des fibres ligneuses disposees en plusieurs 

 series, alteniautes entre elles, et prenant par pression la 

 forme d'ar^oles hexagonales.' — (Tableaicx des Genres, Sfc.j 

 p, 76.) Their appearance in my sections cannot be better 

 described than by the above sentence. None of the speci- 

 mens which I have examined exhibit any traces of the cen- 

 tral punctuation, which, in tue existing coniferse, charac- 

 terises each areola. In the recent Araucariae it is generally 

 distinct; in A. Brasiliensis it is very curious, being of a cru- 

 cial form, but the two elongated and traversing limbs of the 

 cross are not on the same plane, being apparently on oppo- 

 site sides of the intervening lenticular disk. Either this 



