66 Elkins and Wieland — On Devonian Wood. 



Preparation of Material. — Concerning the preparation of 

 this material, Dr. Wieland says : 



" The initial trial section was a transverse one cut from the 

 entire specimen, 6X4 centimeters in area, and showed that the 

 tissues had not been subjected to decay, although with the excep- 

 tion of a central area of about 2 x 1*2 centimeters, the cell walls 

 had been crushed together into a nearly dense mass. Carefully 

 oriented sections were next cut from the well-preserved central 

 portions of the specimen, as thus indicated. As completed these 

 are of exquisite beauty, and yield all the essential structural 

 details." 



The dimensions of the sections from the area of perfect con- 

 servation described here are : transverse, 25 X 15 mm ; radial, 

 20 X 13 mm ; tangential, 12 X H mm . These sections must have 

 been cut with the very finest skill since they easily permit 

 study under a 1/12 oil immersion focussed through the entire 

 thickness, structure details being sharp over the entire section 

 and from surface to surface. 



Description of Material. — Before describing the material in 

 hand, it may be of convenience to the reader to briefly recall 

 the generic characters of Cordaitean wood.* The wood is 

 made up entirely of tracheids. In the protoxylem they are 

 spiral and scalariform ; transition stages occur leading to the 

 characteristic pitted tracheids of the secondary wood. The 

 tracheids are conspicuously rectangular in cross section and 

 occur in regular, radial rows. Hexagonal bordered pits appear 

 only on the radial walls of the tracheid in from one to five 

 vertical rows. This primitive multiseriate arrangement of pits 

 is however likewise an Araucarineous feature. Penhallow in 

 North American Gymnosperms speaks of the hexagonal form 

 and compact arrangement of pits as being two constant Cor- 

 daitean characteristics. Growth rings, when present, are for 

 the greater part obscure. Medullary rays are rather numerous, 

 usually uniseriate, though often partly biseriate. The ray cells 

 are mostly of one kind, long and thin walled ; the terminal 

 walls are oblique or curved ; the lateral walls are alone 

 provided with bordered pits. Specialized resin canals are 

 wanting in the wood, though in one species, Cordaites materia- 

 rum, resinous plates occur in the tracheids near the rays. 

 Wood parenchyma is unknown. f The secondary wood;): of 



* Penhallow, D. P.; Notes on the North American Species of Dadoxylon. 

 Trans. Eoy. Soc. Canada, vol. vi, sec. iv, p. 61, 1900-1901. 



f Penhallow, D. P., North American Gymnosperms, p. 57, 1907. 



X Coulter, J. M., and Chamberlain, C. J., Morphology of Gymnosperms, 

 p. 165, 1910. [Seward and Scott.] 



Thomson, E. B., On the Comparative Anatomy and Affinities of the Arau- 

 carineae. Phil. Trans. Eoy. Soc. of London, ser. B, vol. cciv, pp. 1-50, pi's 

 1-7. May, 1913. 



