Barber,— Cupressinoxy Ion vectense, 353 
pits are much less abundant, and are rare or absent in the 
Pinus group. 
The torus, so well seen in certain tangential pits, is still 
more clearly defined in the larger pits on the radial walls 
(Figs. 11 and 12). These, examined in tangential sections, 
frequently show the torus as a dark line suspended in the 
lens-shaped cavity of the pit or closely applied to one side 1 — 
positions which might lead to interesting speculations as to 
the condition of the wood at the time of petrifaction 2 . 
Medullary Rays. 
The medullary rays figure conspicuously in every published 
description of fossil Coniferous wood. While in Dicotyledons 
they are composed of similar elements but differ widely in 
form, in Conifers they are very uniform in shape but differ 
greatly in their component parts. This has led to a minute 
study of them in the latter class of woods. In the first place 
there is their difference of composition. Some of them have 
tracheidal as well as parenchymatous elements, and this 
difference is regarded as an excellent diagnostic character. 
Those woods further which possess vertical resin-ducts usually 
also have radial ones in certain of the medullary rays. The 
latter are then compound and are more than one cell broad. 
In living Conifers which have no resin-ducts, the medullary 
rays are simple and consist of a single vertical layer of cells. 
The two-rowed medullary rays, although occasionally met 
with, are rare 3 ; but they are much more frequently found 
in fossil woods without resin-ducts, and this constitutes one 
of the differences between recent and fossil species 4 . 
1 The torus is well seen also in Sequoia canadensis , Schrtr., and Pinus succinic 
fera, Con wentz. 
2 Strasburger, 1 . c., p. 32 ; also Russow, Zur Kenntniss des Holzes, insbesonderheit 
des Coniferenholzes, Bot. Centralblatt xiii, 1883, p. 37. 
3 Beust, 1 . c. 
4 Kraus, Mikr. Unters., mentions Cupressinoxylon jissum. Araucarian woods 
with two-rowed medullary rays are called Pissadendron. Among woods with 
resin-ducts, Strasburger mentions Larix as not infrequently having double medullary 
rays without resin ducts. 
