Oliver . — The Ovules of the older Gymnosperms . 467 
the lower Cretaceous. In the apparent retention of old features 
it exceeds either Taxus or Cephalotaxus , and its inaccessibility 
as an object of detailed investigation has left a regrettable 
lacuna in our knowledge of the Taxaceae. Whilst all details 
are reserved for treatment in a special memoir 1 , certain of 
the facts of its ovular morphology may be outlined here. 
Already in the winter buds the rudiments of nucellus and 
integument are discernible. By the beginning of May the 
latter overtops the former. Towards the end of this month 
basal stretching ensues, so that nucellus and integument are 
raised up slightly from the enclosing scales. From this inter- 
calated zone a circular cushion projects, this is the future 
arillus. At the beginning of June the buds open, exposing 
the micropyles, and pollen is collected in the usual way. The 
arillus now grows rapidly and meets above the micropyle 
before the end of July. By this time pollen-tubes have 
developed, and these reach the embryo-sac early in Sep- 
tember. Before the winter resting-period pro-embryos have 
been formed in the archegonia, whilst the base of the young 
seed has undergone considerable expansion. This expansion 
and further embryonic development is continued in the follow- 
ing spring. The most striking phase is that shown in July, 
when enormous expansion of the seed-base is manifested. This 
is followed by the differentiation of the stone, and by the 
autumn the drupe-like seed ripens and falls. During this 
second year a marked rumination of the endosperm develops, 
but this feature need not be described here. 
The vascular system, indicated in the first year by strands 
of desmogen, undergoes no marked degree of differentiation 
till the approach of seed-ripening. Its distribution is indicated 
in red in Fig. 13. This diagram is a longitudinal section of a 
ripening seed cut in the principal plane, but the central light- 
red area must be regarded as convex as it represents the 
exposed surface of the nucellus. At the top of the figure 
1 For some time I have, in conjunction with Miss Edith Chick, been occupied 
upon an investigation of this genus, and it is with her sanction that I am enabled 
to utilize some of our results here. 
K k 
