604 REVISION OF ARAUCARIOXYLON — KNOWLTON. 



1874, lie however mentions * four or five additional species, that had 

 been made known since the publication of the first notice, mostly by 

 Dawson from the carboniferous of Canada and Nova Scotia. In the 

 latter volume he speaks of the investigations that were just being un- 

 dertaken by Bronguiart on the silicified seeds of St. Etienne, and also 

 of a verbal communication made to the Academy of Sciences by Grand 

 'Eury concerning the discovery of forests of Cordaites in the Loire basin. 



The results of Grand'Eury's investigations were published in 1877 

 in his now justly celebrated "Mernoire sur la Flore carbonifere du De- 

 partment de la Loire." From this copious material, fortunately discov- 

 ered in Central France, he was able for the first time to supply a 

 complete history of Cordaites, including the leaves, branches, trunks, 

 flowers, and seeds. 



As the internal structure of the trunks and branches is the primary 

 subject under discussion, our attention will hereafter be given entirely 

 to this phase or the subject. The center of the trunk Graud'Eury 

 found to be occupied by a very large pith, with which he was able to 

 connect the heretofore largely problematical organisms known as Artisia 

 ( Sternberg ia Artis). Artisia, as generally kuown, consists of a struct- 

 ureless cylinder, marked on the outside by numerous ridges or wrinkles, 

 which as long ago as 1840 Dawes had suggested might be the cast of 

 the medullary cavity of some plant possessing a pith similar to some 

 living members of the Juglandaeeae, Euphorbiacea?, etc. Dawson had 

 also obtained specimens from the Carboniferous of Canada that 

 pointed to the medullary origin of Artisia, but was in doubt as to the 

 plants uniformly producing them, and from exceptionally well preserved 

 specimens in England Williamson was able to establish the connection 

 between Artisia and an undoubted Dadoxylon, but it was left for 

 Graud'Eury to show its connection with Cordaites. According to him 

 the larger trunks inclosed an Artisia pith having a diameter of from 

 .05 to .08 or even .10 mm , while in the branches it varied from .03 to .01 mm . 



Surrounding this pith was a dense woody zone, which was in its turn 

 surrounded by a very thick bark. This woody zone on its inner edge, 

 when in contact with the pith, was composed of trachei'ds which were 

 provided with transverse striations and forming typical pseudo-scal- 

 ariform tissue, gradually changing outwardly to true punctate tissue. 

 These puuctations were arranged iu from one to four or five longitud- 

 inal rows, and when in more than one row becoming alternate and 

 hexagonal by mutual pressure. These pits were perforated by an ellip- 

 tical or circular pore, the form of the inner pore depending evidently 

 somewhat upon age and also upon the state of preservation of the 

 specimen. These punctations were confiued to the radial walls of the 

 cells, and, unlike some living Conifers, each cell was always provided 

 with them. Percoursing betweeu these trache'ids were numerous short 

 medullary rays connecting the pith and bark. 



# Pal. V^g., Vol. ill, pp. 560-564. 



