A Jurassic Wood from Scotland. 
207 
Podocarpineae, the reverse is true—the torus is much reduced (or 
rudimentary ?) and distinctly smaller than the pore ; while in the 
normal wood of the living Araucarineae, as in the Cordaitales, 
Cycadales and ancient gymnosperms generally, it is lacking 
altogether. In a number of fossil Araucarians, however, it has 
been described—e.g. Paracedroxylon (16) where it is of the same 
type as in this specimen in question. Another feature which in 
this specimen resembles the conifers and Gentales (18) is the 
presence of trabeculae. These should be distinguished from “ bars 
of Sanio,” or “ rims,” as Groom (7) prefers to call them. By the 
former are meant lignified bars which cross the lumen of a cell; 
by the latter, cellulose thickenings embedded in the substance of 
the wall itself, between the bordered pits. Trabeculae occur 
indiscriminately throughout the coniferous series ; rims of Sanio 
are present in the Abietineae, Cupressineae, Podocarpineae and 
Taxineae, but never in the Araucarineae, living or fossil. They are 
quite unrepresented in this specimen. In addition to the trabeculae, 
there are other cross partitions, occurring very abundantly and 
easily recognized by their thinner, more delicate walls, and generally 
curved contour, Figs. 2, 3 and 4 show how extremely numerous 
they are. These are unquestionably tyloses, for in tangential 
section it is possible to obtain stages of their outgrowth from the cells 
of the medullary rays. Preparations were made from all parts of the 
stem—near the pith and at least in the 50th year, and from each 
end—but the tyloses were uniformily present. The subject of 
tyloses in the tracheides of conifers has long been a disputed point, 
Molisch (12) stating that they are altogether lacking, while Raatz 
(13) considers that wounds induce their formation in various species 
of Pinus, Picea, Larix, Thuya, etc. In 1908 Chrysler (3) re-investi¬ 
gated the whole question and, after a comprehensive examination 
of numerous representative genera, concluded that Pinus is the only 
genus where tyloses occur, and then only in the heart wood of the 
root and the cone axis. Wounds, in general, bring about a better 
development in these restricted regions, but do not cause them to 
appear in other regions or other genera. This condition is strikingly 
different from that recorded by Brooks and Sharpies (2), where the 
traumatic stimulus given, in this case by a fungus, caused the 
formation of tyloses in the vessels of Hevea brasiliensis, whereas in 
the healthy wood they are completely absent. Bailey (1), however, 
has seen indications of them in the normal stem wood of several 
species of Pinus, and Conwentz (4) has described them from Eocene 
material. In none of these cases are the tyloses so abundant as in 
