452 Oliver . — The Ovules of the older Gymnosperms. 
with a fairly complicated vascular system. When we pass 
from these most archaic of living Phanerogams to the various 
Gymnospermous seeds found in the palaeozoic rocks, seeds 
which there is every reason to believe possessed an even 
less specialized type of zoidiogamy than obtains in recent 
Cycads, we are struck with the importance and dimensions of 
the pollen-chamber and with the very complicated vascular 
system which embraces the body of the nucellus. These 
older seeds needed to be complex to neutralize the disadvan- 
tages of their ancestry. In them, whilst the macrospore is 
retained, the microspore still liberates spermatozoids on the 
nucellus. The arrangement, viewed in the light of what 
we find in more recent plants, may be a clumsy makeshift, 
but it was probably an essential link in the evolution of more 
perfect arrangements. The central principle of zoidiogamy 
is still there, hedged about by contrivances so that it may be 
carried out, independent of chance water-supply, by land- 
growing plants. With the appearance of siphonogamy these 
contrivances became obsolete, and the modern ovule is a 
reduced and comparatively simple structure from which traces 
of the ancestral history have in large degree vanished. 
The object of the present paper is to draw attention to 
the details of some of these older seeds, and to trace the 
modifications that seem to have occurred pari passu with 
the evolution of more perfect methods in the transportation 
of the male cells. And in so doing it is hardly possible 
to ignore certain other changes that have taken place in 
the structure of the ovule, changes involving an enlargement 
of its functions so that it has become as well a temporary 
resting-place or brood-chamber for the embryo. The dis- 
cussion in the following pages will include a consideration 
(i) of the ordinary palaeozoic types of seed so well repre- 
sented in the French permo-carboniferous and described by 
Brongniart and Renault ; (2) of Lageno stoma, a peculiar type 
found in the lower coal-measures of Lancashire and York- 
shire, and standing somewhat apart from the French palaeozoic 
seeds ; (3) of recent Cycads ; and (4) of Torreya . a remark- 
