1102 Thompson , — The Anatomy and 
of pits typically Coniferous, tangential pits, bars of Sanio, and occasionally 
by tertiary spirals, trabeculae, and resin plates. 
The vessels possess all the features just enumerated for the tracheides, 
and have also perforations which represent bordered pits. The transitions 
between tracheides and vessels are remarkably complete, all stages in the 
disappearance of torus and border being visible even in single elements. 
The vessels are very few in number and of a primitive character in the 
seedling, and more numerous though of the same character in the first- 
formed secondary wood of the branches. Fusion of perforations may be 
observed rarely. 
The wood-parenchyma cells, which occur abundantly either scattered or 
in tangential rows, resemble tracheides in size, shape, lignification, and some- 
times in pitting, and have probably been derived from tracheides. They are 
often multinucleate. They appear to resemble most the so-called fibrous 
cells of Angiosperms. 
The medullary rays of the first-formed secondary wood are uniseriate, 
and from these the broad rays of the adult are derived either by simple 
enlargement, addition through the transformation of tracheides to ray par- 
enchyma, or by compounding. The latter process is the same as in 
Dicotyledones. False rays are common. The individual cells are lignified 
and pitted like those of Dicotyledones. The broad rays have a retarding 
influence on the growth of the surrounding wood. 
The bast is typically Gymnospermous. 
The cortex is abundantly supplied with chlorophyll and functions as 
a leaf. The stomata in the epidermis of the stem are numerous, and are 
confined to furrows between projecting ridges due to hypodermal bundles. 
The leaves are small and non-functional, except a few on the seedling. 
The vascular bundles are two in number, small and endarch. Transfusion 
tracheides are common. At the tip of the seedling leaves the transfusion 
tracheides develop centripetally and become more like centripetal wood. 
The idea of Cycadalean and Bennettitalean affinity receives little 
support from the anatomy of Ephedra. On the other hand, there are many 
points which are opposed to it, and in favour of Coniferous relationship : the 
arrangement of the primary vascular bundles, double leaf-trace, arrangement 
and structure of pits on the tracheides, bars of Sanio, tertiary spirals, trabe- 
culae and resin plates, primitive uniseriate lignified rays, wood parenchyma, 
and endarch vascular bundles of the leaf. The Gnetales do not appear to 
have arisen from any modern group of Conifers, but rather from or close to 
the base of the Coniferous line. 
An Angiospermous affinity is indicated by the possession of true 
vessels, broad rays, formation of broad rays by fusion, and separation of the 
leaf-traces on the stem. 
This investigation has been carried on by the writer in the Phanero- 
