546 
Gibbs. — On the Development of the 
vascular strands can be traced separately to the base of the same. This 
distinctiveness is shown in the section figured, by the separation of the 
two resin canals, viz. that of the sterile bract to the right and that of the 
ovuliferous scale in the centre. Only a trace of the vascular bundle of the 
fertile bract is visible (Fig. 79) to the left, but that is sufficient to show how 
widely it is separated from that of the ovuliferous scale with its inverted 
orientation. 
In transverse section of the same stage, a microphotograph (PI. LI 1 1 , 
Fig. 80) shows a section taken through the base of the nucellus where the 
two bundles spread round the base of the ovule. It is slightly oblique, but 
the foliar structure of the scale comes out well. The lamina of the fertile 
bract appears on the dorsal side to the left (Fig. 80). 
A prothallus, showing an embryo, was sectioned. The structure was 
identical with that described for P, imbricata (see p. 530). 
P. polystachya. 
Morphology. This material was collected from a large tree growing 
in the Buitenzorg Botanic Gardens. The leaves are long and Willow-like, 
aggregated towards the end of the branches. The strobili arise in the 
axils of the foliage leaves and consist of apparently two bracts, of which 
one is fertile. The unmodified lower bracts are no longer present (PI. L, 
Fig. 35). The ovules all show different stages of pro- and embryo formation 
(Figs. 36 and 37, and PI. LI, Figs. 38 and 39). 
Histology. Some of the ovules were much smaller, suggesting earlier 
stages (PI. LI, Fig. 41), but, on sectioning, these showed sterile prothallia, 
in which pollen-tubes, however, had penetrated the whole length of the 
persistent apex of the nucellus in each case (PI. LI, Fig. 42,/. /.). 
In both fertile and sterile prothallia there is a well-marked epidermis, 
showing small uninucleate cells which contain little or no starch (PI. LI, 
Fig. 39 b , epi.) with thickening of the outside cell-walls. Coker has also 
described and figured a similar layer for P. coriacea ( 15 , p. 97). This 
epidermis in the sterile prothallia was folded in and out over the apex and 
even into the neck of the archegonial cavity, owing to contraction of 
prothallial tissue. 
Below these convolutions is a cavity (PI. LI, Fig. 42, dis. arch.) where 
the archegonia would normally occur, but of which no trace was to be 
seen. In the central cylinder of small cells which reached below the 
cavity to nearly the base of the prothallus were a great many tracheides 
(Fig. 42, tra.) and Fig. 43). Neither the central cylinder nor the rest of the 
prothallus contained starch in the cells, though most of them were binucleate. 
This absence of storage contents was strikingly shown in a similar prothallus 
cleared in cedar-wood oil. The transparency was so great that the cylinder 
of small cells showed clearly through the centre, giving a very slight opaque 
effect, otherwise the prothallus would have been invisible. On cutting, 
