1912} THOMSON & ALLIN—PITYOXYLON 341 
The radial pitting of the tracheids is illustrated in text fig. 1B, 
which is taken from the radial section at the place marked d in plate 
fig. 2. The bordered pits are “‘in 1-3 rows, chiefly 2 rows.’”? They 
are alternate in arrangement, and flattened, as it were, by mutual 
contact, often presenting a more or less hexagonal outline. The 
orifice is not “probably round,” however, though such appearances 
are quite common where the preservation is defective (text fig. 1C). 
Fic. & Fic. 2 
GS. 1-2.—Fig. 1, from radial cross-section: A, medullary ray cells; B, radial 
pitting of tracheids (from plate fig. 2 at d); C, radial pitting in tate of F tion; 
X250; fig. 2, from tangential section (plate fig. 3 at @): showing tissue continuous 
and also tangential pitting adjacent to the ray; X100 
Even here transitions to the normal type can be observed. It is elon- 
gated and obliquely placed, the two orifices on contiguous walls in 
some cases showing at right angles to one another (first and second 
tracheids from the right in text fig. 1B). This is not the character 
of the radial pitting of Pityoxylon as defined by Kraus (SCHIMPER 
and SCHENCK 6, p. 852), ‘‘Aréoles unisériées; opposées lorsqu’il y 
en a deux rangs,” but that of an Araucarioxylon or cordaitean form. 
The presence of horizontal resin canals upon which “P. Cha- 
sense” is referred to the genus Pityoxylon is exhibited, according 
* Fifty counts were made in different parts of the radial section with the following 
result: r1-seriate 16 per cent, 2-seriate 62 per cent, and 3-seriate 22 per cent. 
