[PENHALLOW] NORTH AMERICAN SPECIES OF DADOXYLON 61 
1877, 257, 260 ; G6ppert, Die Foss. Flor. der Perm. Form, 1864-1865, 
249-259 ; Gôüppert, Die Flor. der Sil. Dev. und unt. Kohlenform., 
1859, 548-550; Géppert, Die verst. Walder im nord. Bohem. und 
Schles., 1859, 7, Pls. I. & II.; G6ppert, Foss. Flor. des Ubergangsg., 
1851, 252-256 ; Williamson, Org. of the Foss. Pl of the Coal Meas., 
Trans. R. Soc., 1872, IV., 377; Trans. R. Soc., 1876, VIII., 222, Pls. & 
Figs.; Gôppert, Foss. Conif., 1850, 230-236; Engler & Prantl. Gen. 
Plant, II., 1, pp. 26, 116 ; Solms-Laubach, Foss. Bot., 1891, 104-122 & 
80-84; Witham, Int. Struct. Veg. Foss., 1833. 
Transverse.—Pith of the Sternbergia type: the cells large, thin-walled, often 
resinous. Growth rings when present obscure, rarely somewhat 
conspicuous. Specialised resin cells and canals wholly wanting 
except in the bark where they take the form of tubular, branching 
canals without epithelium, extending in the general direction of the 
stem axis. Tracheids in regular, radial rows, conspicuously squarish. 
Radial.—Elements of the protoxylem spiral and scalariform, and often show- 
ing a graduated transition into tracheids with bordered pits. 
Tracheids with hexagonal, bordered pits throughout, on their radial 
walls only, in 1-5 rows. Ray cells usually of one kind only; the 
upper and lower walls thin and not pitted; the terminal walls thin, 
not pitted, generally curved; the lateral walls with bordered pits. 
Tangential.—Medullary rays rather numerous, 1-seriate or often 2-seriate in 
part. 
SYNOPSIS OF SPECIES. 
The following synopsis is given provisionally as an aid to identifica- 
tion of the various species, without implying the absolute value of the 
differential characters. 
I.—Growth rings present. 
1. C. pennsylvanicum. 
Il.—Growth rings obscure or obsolete. 
A. Ray elements of two kinds, tracheids and parenchyma. 
Bordered pits in 2-3, rarely four rows. 
Ray cells (tang.) oval or oblong, often narrow. 
2. C: Clarkii. 
B. Ray elements of one kind only. 
Bordered pits in groups of 6-15. 
Pits on the lateral walls of the ray cells 3-6, chiefly 4 per tracheid. 
3. C. Newberryi. 
Bordered pits in one row, compressed. 
Ray cells (tang.) broad, round. or squarish. 
4. C. recentium. 
Bordered pits in 1-3, chiefly 2 rows. 
Ray cells (tang.) broadly oval. 
Ray cells about 31-57 mic. board. 
