[PENHALLOW] NORTH AMERICAN SPECIES OF DADOXYLON 63 
“ Les espèces-type de ce genre sont les Dadoxylon Brandlingii et 
Dadoxylon tchihatcheffianum,”* and with respect to the former at least, 
this view has been generally recognised. It is therefore desirable that 
the histological characters of this species should be passed in review in 
the present connection. 
The material in hand was derived from St. Etienne, France, and 
may therefore be regarded as typical. Excellent figures of this plant, 
with respect to its internal structure, have already been given by Zittell, 
Schimper & Schenk; by Witham and also by Goppert, and with these 
our photographic figures agree. But in the various descriptions so far 
given, certain details of importance are not taken into consideration, 
and these are now embodied in the diagnosis presented here. One of the 
best descriptions of the plant as already recorded, is that given by Unger 
to the following effect? :— 
“D. ligni stratis concentraticis obsoletis, vasis amplis leptotichis, 
poris bi-tri-quadriserialibus contiguis, radiis medullaribus simplicibus 
aut rarius compositis e cellulis 1-17 superpositis formatis.” Some of 
these details properly belong to the description of the genus, for which 
we reserve them. To the others we add such as may serve to clearly 
differentiate this species from the others now under consideration, and 
at the same time preserve its typical character. 
Transverse.—Pith cells about 62 mic. broad, the walls about 16 mic. thick. 
Tracheids somewhat elongated radially, about 25 x 38 mic., the walls 
about 6 mic. thick. 
Radial—Ray cells more or less conspicuously contracted at the ends; short, 
equal to about 1-3 tracheids ; the pits on the lateral walls oval or 
round, narrowly or obscurely bordered, 1-3, chiefly 2 per tracheid. 
Bordered pits typically hexagonal, in 1-3, chiefly 2 rows through- 
out the tracheid, and in the region of the protoxylem showing numer- 
ous and striking transitional forms from scalariform vessels ; 12°5 
mic. broad. 
The pith shows characteristic Sternbergia structure, the cells 
flattened vertically. 
Tangential—Rays low, narrow, 15:5 mic. broad; the oblong cells 1, or some- 
times 2-seriate in part. 
1 Dict. univ. d’Hist. nat., 1849, 97. 
2 Gen. et Spec. Pl. Foss., 1850. 
