Oliver . — The Ovules of the older Gymno sperms. 465 
The arrangement of the strands in Cycas Rumphii is in 
close agreement with that shown by Warming to exist in 
Cycas circinalis 1 . But many other different types obtain 
according to the manner of joining up of the vascular strands 
at the chalaza. Thus in Zamia sp. (a complex case) the 
ovular supply is constituted from two bundles, each of which 
forks and joins again as they pass into the chalaza. Of these 
two reunited bundles, one supplies one-third of the integument 
and nothing more ; the other gives off two bundles which 
supply the remaining two-thirds of the integument, whilst its 
continuation breaks up, supplying two-thirds of the nucellus. 
The remaining one-third of the nucellar ring is derived, 
relatively high up, from one of the two integumental bundles 
which arose lower down from this same system. 
These varying types of chalazal branching seem consistent 
with the assumption that the whole of the body of the ovule, 
below the level at which the nucellus becomes free, is phylo-' 
genetically younger than its apical parts — that between the 
original ovule and its insertion a new region has been inter- 
calated. This suggestion is embodied in Figs. 1, 2, and 3. 
In Fig. 1 is shown the conjectured ancestral palaeozoic type 
as described in the first section, but so far modified by the 
assumption of a plane of symmetry as to bring it in touch 
with a Cycadean ovule such as that of C. Rumphii . In Fig. 2 
the possible mode of intercalation of a new zone is indicated 
by the broken lines (included under the bracket b .), all the 
structures of nucellus and integument being continued across 
this new zone. As the zone of stretching lies below the 
insertion of the nucellus, the gap between nucellus and integu- 
ment finds no place in the new insertion. For the rest, how- 
ever, it is a mere extension of the tissues of integument and 
nucellus. An ideal case is represented in Fig. 2, perhaps 
never realized, in which the bundles are all connected at the 
chalaza exactly as in the palaeozoic type (Fig. 1). With 
the basal extension of the ovule fresh distributions of the 
1 E. Warming, Recherches et remarques sur les Cycadees, 1877, P* 21 and PI. Ill, 
Figs. 6-12, 
