562 
Gibbs. — On the Development of the 
ovules in the strobili of each period. It is probable that this feature is 
associated with the great reduction in the number of fertile bracts to each 
cone. The same fact has been recorded for Ginkgo. 
Histological Results. 
The ovuliferous scale shows the complete organization of a foliage leaf 
with epidermis, stomata, and mesophyll tissue. It is provided with a well- 
developed vascular system with inverted orientation, and accompanied by 
resin canals. 
In § Dacrycarpus a hypodermal sclerotic layer is present in both the 
ovuliferous scale and the foliage leaves. 
In § STACHYCARPUS, on pollination, groups of stone cells form a regular 
zone in the mesophyll tissue. In P . ferruginea these were also present in 
the foliage leaves. 
The cells of the mesophyll show secondary thickening throughout the 
group, which is initiated before fertilization. 
The vascular system of the ovuliferous scale consists of two bundles 
(P. vitiensis four), each accompanied by a resin canal. These arise each at 
the extreme apex of the scale in a hypodermal group of tracheides, as 
is also the case in the foliage leaves. They branch in a ring below the 
insertion of the ovule, half-way down the scale. From this ring secondary 
branches may run into the lamina of the scale, so encircling the ovule ; these 
branches stop half-way down the lamina or continue right to the micropyle, 
and are always terminated by groups of tracheides. 
Below the ovule the main bundles separate, and by a gradual semi- 
rotation the phloem becomes peripherally placed when they insert themselves, 
one on each side of the vascular strand of the fertile bract, on to the ring 
of bundles in the strobilus. 
Resin canals accompany each bundle on the phloem side. These are 
very active, with well-developed epithelium, and evidently play an important 
part in the metabolism of the scale. Their function gradually ceases on the 
organization of starch formation in the female prothallus. In later embryo 
stages the epithelium is no longer traceable. 
The resin canals limit the tissue of the integument in the plane of the 
mesophyll tissue of the scale. 
The integument shows basal growth, and its small regular cells stand 
out well from the irregular mesophyll of the scale. Long lignified hypo- 
dermal cells are differentiated in the apex, at the micropyle, at pollination, 
at which stage also a nutritive zone of starch and tannin cells ( cellules tanni- 
feres of Tison) is laid down round the base and sides of the nucellus till the 
prothallus is fully organized, when, as is the case with the resin canals, the 
