Holden . — Jurassic Coniferous Woods from Yorkshire. 539 
cells, where in contact with each other, are heavily pitted, precisely as in 
the Abietineae. The pits from ray to tracheide are piciform, usually one 
or two to each cross-field. There is never any wood parenchyma. Figs. 19, 
20, and 21 are of a lignite from Scarborough, showing similar structure. It 
differs in that the tracheides are smaller, the radial pits are uniserial, 
and always closely approximated, and usually the rays have but one pit to 
each cross-field. The most striking feature of this specimen is the large 
number of tyloses in the tracheides (Figs. 20 and 21). Several lots of this 
material were found, and in all the tyloses are present. 
From the absence of cellulose bars of Sanio in all the specimens 
of this type, it is evident that we are dealing here with another Araucarian 
Conifer, which in view of the ray pitting must be transitional between that 
group and the Abietineae. The wood is indeed identical with that 
described by Jeffrey as Araucariopitys , and by Gothan as Protocedroxylon 
araucarioides , even to the tyloses in the tracheides. Jeffrey considers this 
an Araucarian type, while Gothan, from the structure of the rays, considers 
it Abietineous. As pointed out above, such thick-walled pitted rays 
are present in the cone axis of the living genus Agathis and may be recalled 
as a result of wounding in both Araucaria and Agathis . Since the cone 
axis has been shown repeatedly to retain ancestral conditions, and traumatic 
tissue to recall them, it seems entirely logical to conclude that the living 
Araucarineae are derived from ancestors which had thick- walled pitted 
rays. If so, there can be no doubt that this Jurassic wood under considera- 
tion is one of these ancestors. Since the term Protocedroxylon implies 
Abietineous affinities, it seems better to change it to Metacedroxylon , though 
retaining the original specific name of Gothan, and to call this wood 
Metacedroxylon araucarioides. It is interesting to note that Lignier 
(op. cit.) has described as Araucarian several similar specimens, with 
Abietineous pitting of the rays. His diagnosis depends on the character of 
the tracheary pitting. As mentioned above, approximated and flattened 
pitting are not invariably characteristic of the living Araucaria and Agathis, 
being replaced in the seedling by the scattered and circular pits which con- 
stitute the Brachyoxylon type. Since the seedling, like the cone axis, has 
in numerous instances been shown to perpetuate ancestral conditions, 
it seems justifiable to assume that flattened pitting is not the primitive con- 
dition for the Araucarineae, and will be less and less reliable as a diagnostic 
feature in progressively older geological horizons. Thus by a process 
of elimination, we are led to adopt the cellulose bars of Sanio" as the only 
sure criterion for diagnosing coniferous woods. Accordingly, Metacedro- 
xylon araucarioides cannot be other than an Araucarian Conifer. 
Locality: Whitby and Scarborough. Horizon: Oolite. 
,, Robin Hood’s Bay. „ Lias. 
