72 Elkins and Wieland — On Devonian Wood. 



nearly clear silica, the pit walls being distinctly dense. Sim- 

 ilarly arranged cross-like orifices are present in Pityoxylon 

 Chasense as described by Thomson and Ailin,* who claim that 

 this latter species is of Cordaitean affinity and not related to 

 the Abietineae. The AT-like aspect of the apertures in the pits 

 also characterizes Araucaria brasiliana, as long since figured 

 by Winklerf ; while Goeppert noted this feature in fossil forms. £ 



The presence of pits in the walls of the tracheids may be 

 seen, though with less distinctness, in transverse or tangential 

 sections. The walls, when viewed with a high power of the 

 microscope, exhibit series of broken, bulging outlines, which 

 plainly indicate the presence of the pits (figures 6 and 8). The 

 position of the middle lamella is also absolutely distinct with 

 oil immersion ^ oc. 2 in all the sections (figure 6). Whether 

 or not a torus is present I cannot now say. 



The medidlary ray, because of the large amount of dark 

 colored material in many of the cells, is a conspicuous feature. 

 The rays, viewed in a transverse section, are very similar, 

 being usually one cell in breadth, though sometimes two cells 

 wide. The biseriate ray of this species is, however, always 

 partly uniseriate (figure 7, photomicrograph 3). A radial sec- 

 tion shows that the rays, though narrow, are of considerable 

 depth as appears in figure 9. In a tangential section the ray 

 is seen to vary from a single cell in depth and breadth to a ray 

 forty cells in depth and from one to two cells in breadth. 

 Between the two extremes all gradations may be found (cf. 

 figure 7). Dadoxylon Pedroi, of Zeiller, however, exceeds 

 the Indiana species in the remarkable height of its rays, which 

 sometimes consist of even fifty superposed cells.§ 



The ray cells are parenchymatous^ long and thin walled. 

 Using the tracheid width as a unit of measurement the ray 

 cells range from two to eight tracheids in length ; the terminal 

 wall is vertical, curved or oblique. A tangential view of the 

 wood shows the ray cells to be rectangular, oval or circular in 

 cross-section and of exceedingly variable size. The horizontal 

 walls of the outermost cells are irregular, seeming to extend in 

 pointed projections between the tracheids (cf. photomicro- 

 graph 3) ; this often gives the appearance of an abrupt narrow- 

 ing at the ends of the ray cells, which is really a return to the 

 normal diameter. Through the lateral walls, the ray cells 

 communicate with the tracheids by means of pits, which are 

 simple in the ray cell wall and bordered in the tracheid wall ; 



* Thomson, R. B., and Allin, A. E., Do the Abietineae Extend to the Car- 

 boniferous? Botanical Gazette, vol. liii, No. 4, April, 1912. 



\ Winkler, C. Zur Anatomievon Araucaria braziliensis, Botanische Zeit- 

 ung 1872, p. 583, (Tafel VII). 



J Goeppert, H. R., Monographic der Fossilen Coniferen, Leiden, 1850. 



§ Zeiller, M. R., Note sur la Flore Fossile des Gisements Houillers de Rio 

 Grande do Sul., Bull. Soc. G<k>l. de France, Serie 3, Tome 24, p. 624. 1896. 



