Oliver. — - The Ovules of the older Gymnosperms . 471 
foramen (cf. Fig. 12, /.). The flanks continue their course 
for an appreciable distance in the pulp outside the stone, 
and end in a mass of transfusion-tracheides at a point a little 
below the level at which the arillus becomes free from the 
integument (Fig. 12, t.). 
The remarkable course of the bundles shown in this seed 
suggests a comparison with that found in Cycads and the 
palaeozoic seeds. At first sight Torreya seems so different 
that such a comparison must be vain. But bearing in mind 
the conclusion reached in the section dealing with the Cycads, 
as to the probability of the lower part of the seed being 
phylogenetically younger than the apex where nucellus and 
integument are free, and applying the same principle to 
Torreya, it seems possible to describe the latter in terms 
of the palaeozoic seed. For the purposes of this elucidation 
it is convenient to start with a form slightly modified from 
the supposed ancestral palaeozoic seed as in Fig. 10, a form 
differing from the type (Fig. 1) in that, instead of a single 
supply-bundle entering at the chalaza, we assume that there 
is a pair. Such a seed is shown cut longitudinally in the 
principal plane in Fig. 10. It resembles that given as the 
starting-point of Cycas in all other respects, except that the 
nucellar investment of tracheides is rendered as a continuous 
mantle and not as discrete bundles. (The red shade over the 
nucellus is to be regarded as representing the surface of 
the nucellus covered with its tracheal mantle.) From such 
a type Torreya may be derived by supposing that, at the 
time when a basal stretching of the ovule set in, this was 
accompanied by a marked rotation of the bundles which 
immediately connected with the tracheal plate at the base 
of the nucellus, so that one was carried some 8o° to the right 
and the other a similar amount to the left. This process is 
sufficiently represented in the transitional Fig. n, where the 
intercalated zone (under the bracket b.) is drawn in broken 
lines. It may be said that a marked feature of the evolution 
of this seed was the transverse expansion of the inner part 
of the chalaza which accompanied the general basal extension. 
