Bailey . — A Cretaceous Pity oxy Ion with Marginal Tracheides. 321 
specialized structures have been evolved. Thus modern Hard Pines are 
characterized by the absence of tangential pitting in the summer tracheides, 
and by possessing ray tracheides with dentate and reticulate thickenings, 
structures which occur only in these pines. Recently the writer has called 
attention 1 to the evolution in modern Hard and White Pines of large 
irregular lateral ray pits or * Grosseiporen’ (see Figs. 11 and 12) from pici- 
form pits (see Fig. 10) such as occur in certain primitive living pines (the 
Nut and Foxtail Pines of the south-western United States, Pinus Bunge ana, 
Zucc., and P. Gerardiana , Wallich, of Asia) and Cretaceous pines. The 
‘ Grosseiporen ’ were shown to be formed by the fusion of several small pici- 
form pits into a single large pit. This fusion takes place either by the 
enlargement of the lenticular openings of the piciform pits and their subse- 
quent fusion as is shown in Figs. 7 and 11, or by the gradual reduction in 
thickness of a large portion of the tracheide and parenchyma walls. In the 
latter case the lignified secondary wall of the tracheide often falls away first, 
leaving the ghost-like pit partition intact on the parenchyma side. This 
condition is illustrated in Fig. 12, a radial section of Pinus Jlexilis , James. 
The development of ‘ Grosseiporen ’ or fusion pits does not appear to the 
writer a character of great diagnostic importance, since it is a character 
which is likely to be evolved in all Conifers in which there is a reduction in 
the thickness of the ray parenchyma walls. In defence of this statement it 
is only necessary to call attention to the occurrence of fusion pits or ‘ Eiporen ’ 
in certain Podocarpineae, notably in Dacrydium and in certain ligneous 
remains referred to Araucarioxylon latisporosum by Kraus and Conwentz, 2 
to Cupressinoxylon Barberi by Seward, 3 and to Xenoxylon phyllocladoides by 
Gothan. 4 
If we now turn to the lignite under consideration in this article we see 
that the mere presence of resin canals, of thick-walled, heavily pitted ray 
parenchyma (Abie tine entiipfelung), of piciform lateral ray pits, and the 
absence of wood parenchyma and so-called Araucarian pitting are not in 
themselves sufficient evidence for inferring that we have not to deal with 
a primitive member of the Araucarineae, Abieteae, Taxodineae, or Cupres- 
sineae. The occurrence of ray tracheides appears, however, to exclude the 
Araucarineae, since these structures have never been observed in living or 
fossil forms of this family, furthermore, the occurrence of bars of Sanio 
between the radial bordered pits in the tracheides of our Conifer confirms 
this supposition. Miss Gerry has made a careful study of the distribution 
1 Bailey, I. W. : Anatomical characters in the evolution of Pinus. Am. Nat., vol. xliv., May, 
1910. 
2 Fossile Holzer aus der Sammlung der konigl. preuss. geolog. Landesanstalt, 1882, p. 170. 
3 Jurassic Flora, pt. ii, 1904, p. 61, t. vii, Figs. 1, 4, 6. 
4 Fossile Holzer aus dem Bathonien Russ. Polens. Verhandl. kais. russ. mineral. Gesellsch., 
1906, p. 454. Die fossilen Holzer von Konig Karls Land. Kungl. Svenska Vetenskaps- 
akademiens Handl., Bd. 42, No. 10, 1907. 
