3x8 Bailey . — A Cretaceous Pity oxy lor, with Marginal Tracheides . 
and palaeobotanists, was advocated by Kraus , 1 and divides the Conifers into 
five distinct groups or ‘ genera separated by marked structural differences. 
The ‘genus’ Araucarioxylon , framed to include the Araucarian Conifers, 
of which Agathis and Araucaria are living representatives, possesses closely 
approximated and mutually flattened bordered pits in the radial walls of 
the tracheides, pits which when in more than one row alternate with one 
another. The remaining Conifers in contrast to this possess unflattened 
and non-alternating or opposite pits. Of the four genera which occur 
in this general group, the most distinctive is Pitoxylon , which possesses 
resin canals and is represented among living Conifers by Pinus , Picea , Larix , 
and Pseuaotsuga. Taxoxylon, with Taxns for its type, possesses throughout 
the year’s growth tracheides with well-developed tertiary spiral thickenings. 
Cedroxylon , represented by Cedrus and allied forms, is separated less easily 
from Cupressoxylon ( Cnpressinoxylon ), which includes the Cupressineae and 
Taxodineae, &c., but in contrast to the latter is characterized by the absence 
or feeble development of resin parenchyma. 
According to the classification of Kraus, our lignite would undoubt- 
edly be classified under Pityoxylon since it possesses well-developed resin 
canals. 
The L genera ’ of Kraus have been somewhat modified by Gothan 2 who 
points out that the distribution of resin parenchyma is not a satisfactory 
criterion upon which to separate Cedroxylon and Cupressinoxylon , since 
abundant resin parenchyma occurs in certain forms commonly referred to 
the former. He asserts that the Abietineae possess a distinctive type of 
pitting ( Abietineentiipfelung ) which he uses as a diagnostic character in 
separating the two ‘genera’. The latter ‘genus’ is divided by him into 
five divisions upon the basis of differences in ray pitting. Similarly, Pityo- 
xylon is divided into Pinuxylon , to which are assigned the ligneous 
characters of living pines, and Piceoxylon , which includes Picea , Larix> 
Pseudotsuga , and similar forms. 
The classification of coniferous woods as originally framed by Kraus, 
and as modified by Gothan and others, affords from the point of view of 
the anatomy of modern representatives a satisfactory basis for dividing 
Conifers into natural groups of closely related forms. In addition it has 
been customary in the past to study the affinities of the ligneous remains 
of primitive Conifers by similarity of structure with the genera of Kraus. 
Thus the absence of so-called Araucarian pitting has been considered 
a sufficient criterion for excluding relationship with the Araucarian Conifers. 
The occurrence of heavily pitted ray parenchyma and resin canals has been 
taken as conclusive evidence of relationship with the Abietineae, &c. 
1 Kraus, G., in Schimper’s Traite de pal^ontologie v^getale, Bd. v, pp. 363-85. 
8 Gothan, W. : Zur [Anatomic lebender und fossiler Gymnospermen-Holzer. Abhandl. der 
konigl. preussisch. geolog. Landesanstalt, Neue Folge, Heft 44, Berlin, 1905, pp. 101-103. 
