542 Holden,— Jurassic Coniferous Woods from Yorkshire . 
The presence of these degenerate bars has a not unimportant bearing 
on the diagnostic significance of bars of Sanio in general. As pointed out 
above, their extreme constancy in living forms has led to their adoption as 
the sine qtia non of an Abietineous Conifer. Such has been the assumption 
of Sinnott in the case of Paracedroxylon , of Jeffrey in Brachyoxylon and 
Araucariopitys , and of the writer in these Jurassic woods. Gothan (op. cit., 
p. 32) has questioned the cogency of such reasoning. He denies that there 
is a phylogenetic principle involved in their distribution, and inclines to the 
opinion that their appearance is correlated with the amount of available 
space, — i. e. when the pits are remote, the bar is present ; and when they are 
crowded, the bar is absent. There are two facts militating against the 
soundness of this view. In the first place, as Jeffrey has pointed out ( 7 ), the 
pits in the seedling of Araucaria and Agathis are as remote as in Pinus , 
and yet the bars are always absent ; in the second, the pits in the specimen 
now under consideration are as crowded as those of any Araucarian, and 
yet the bars are clearly present. From these considerations it seems 
evident that Gothan’s explanation is inadequate, and that, on the other 
hand, the diagnostic significance of cellulose bars of Sanio cannot be 
over-emphasized. 
Locality: Scarborough. Horizon: Oolite. 
Podocarpoxylon sp. (Figs. 31 and 32). 
This lignite is also from the vicinity of Scarborough. The rays are thin- 
walled, with one or two piciform pits to each cross-field. Usually the 
tracheary pits are uniserial, but double rows are not infrequent, in which 
case the pits are opposite. Between several of the pits shown in Fig. 31 
may be seen white lines. These are bars of Sanio. They are very common, 
and show all the variations present in living genera, such as Pine. Fre- 
quently they are double, in places they fork at the ends, occasionally they 
are curved, following the contour of the pit, and when the pairs of pits are 
not strictly opposite the bars are at a distinct angle, until rarely they 
become almost vertical. The thin-walled rays exclude this specimen from 
the genus Cedroxylon , and the absence of parenchyma from Cupressinoxylon ; 
the best place for it seems to be in the genus Podocarpoxylon , Gothan. 
The wood of Fig. 32 came from Mr. Lomax. It is less well preserved 
than that last described, but its Abietineous affinities are unquestionable. 
The rays are thin-walled, there is well-marked wood parenchyma at the 
end of the annual ring, and the radial pits of the tracheides are scattered, 
or, when two-ranked, opposite. Bars of Sanio may often be observed. 
Like the last-described wood, this is probably an ancestral Podocarp, and 
should be placed in the genus Podocarpoxylon , Gothan. 
