Holden . — Jurassic Coniferous Woods from Yorkshire. 537 
quite different, being always closely compressed and flattened. On that 
character it is proposed to call this specimen P araphyllocladoxylon arauca- 
rioides. 
P aracupressinoxylon cedroides (Figs. 11-14). 
The sections included under this head were sent by Mr. Lomax. 
Fortunately, a considerable amount of material was available, so that it is 
possible to present a fairly complete account of this interesting wood. The 
pith is homogeneously parenchymatous, without any sclerotic cells or 
diaphragms such as occur very commonly in Mesozoic forms, both Abie- 
tineous and Araucarian (Literature 4 , 6, 7 , 8, and 12 ). The wood consists 
of tracheides, rays, and resiniferous elements. The tracheides are small, 
and rarely have more than one row of pits on the radial wall. In such cases 
they are alternate and compressed. When uniserial, the pits are usually 
scattered and circular, though often flattened (Fig. 13). In no case was 
there any indication of cellulose bars of Sanio. There are also abundant 
tangential pits. The rays are highly resinous, and — an unusual feature 
in Araucarian woods — thick-walled and heavily pitted. Fig. 14 shows this 
character clearly. On the wall next the tracheide the pits are small and 
piciform, ranging from two to several to each cross-field. The resiniferous 
elements are of two sorts — true wood parenchyma, which is scattered 
throughout the year’s growth, and resin-filled tracheides. The phloem is less 
well preserved, but there seem to be no alternately recurring zones of hard 
and soft bast, such as occur in the Cupressineae, for example. In the outer 
bark there are clusters of stone cells, and on the outside a layer of periderm. 
It is evident from a study of the normal tissues that we are dealing with 
an Araucarian Conifer presenting a new combination of Araucarian and 
Abietineous features. Under these circumstances it is extremely fortunate 
that it is possible to investigate its traumatic reaction. One of the sections 
shows, at a short distance from the pith, a distinct wound-cap, from which 
rows of resin canals extend on each side (Fig. 11). These canals persist for 
some distance around the stem and then die out. The nature of this 
abnormal tissue may be ascertained from Figs. 11 and 12. Each duct 
is very wide tangentially, communicates freely with its neighbours, is con- 
stricted at short intervals, and is surrounded by a jacket of thick-walled 
parenchyma cells. The structure of these canals is paralleled exactly by 
those formed after wounding in the genera Abies or Tsuga , and indicate 
beyond doubt that their appearance here is an instance of traumatic 
reversion. It is in the vicinity of the wound that the rays are most highly 
resinous, and the resiniferous elements most abundant. 
The affinities of this wood are not difficult to infer. The absence 
of cellulose bars of Sanio vouches for its Araucarian nature, and its Abieti- 
neous features show it to be another of those transitional forms so abundant 
