528 Gibbs. — On the Development of the 
mesophyll tissues as the lamina of the bract. Most of the cells of the 
mesophyll show tannin and associated starch contents, and many also are 
packed with starch. 
The vascular system consists of two bundles with inverse orienta- 
tion, each accompanied by a resin canal with epithelium. They unite to 
form a ring at the base of the ovule, but separate again and remain dis- 
tinct to the base of the bracts, where the bundles run with normal orientation 
on to the ring of leaf-traces of the strobilus. 
This converse orientation is effected by the rotation of the two 
bundles as they descend the scale, where they form an arc, the phloem 
gradually diverging outwards and the xylem converging towards the 
centre (PI. LIII, P"ig. 77). 
This rotation increases in the passage down the bract bases, until 
the two bundles run on the ring of collateral bundles of the strobilus, 
one on each side of the strand of the fertile bract, with normal orienta- 
tion. The ovular supply bundles in Saxegotkaea, as figured by Tison 
( 57 , PL X, d), insert themselves with a similar semi-rotation on to the 
single vascular strand of the fertile bract, but in Podocarpus the bundles 
remain distinct. 
The integument stands out well from the tissue of the ovuliferous 
scale, owing to its smaller and more regularly arranged cells. At its free 
portion, which forms the micropyle (PI. XLIX, Fig. 8, o.s. inti), the epider- 
mal layer of cells is densely filled with starch and tannin. In the free apex 
at the micropyle the sub-epidermal cells are strongly lignified, staining with 
safranin, are pitted, showing spiral thickening, and elongated in a vertical 
direction (PI. LI, Fig. 58, a.). This feature is characteristic of all the species 
examined. The base of the integument is well defined by a zone of nutri- 
tive cells. Of these cells some are packed with starch, while others contain 
both starch and tannin, the starch grains showing up conspicuously with 
iodine, by their blue coloration, through the tannin (PI. XLIX, Fig. 8, tan. 
and st. c.). A similar zone occurs at the base of the nucellus, a fact Tison has 
also recorded for Saxegotkaea ( 57 , p. 144), designating them ‘ cellules tanni- 
feres ’ ; but he does not specify the presence of starch. These cells appear 
to be initiated at the same stage in both genera, viz. at pollination, with the 
enlarging macrospore ; but in Podocarpus , in conjunction with the zone at 
the base of the integument, their number increases with the growth of the 
female gametophyte until starch formation is initiated in the prothallus. 
Saxton ( 44 , p. 559) in Callitris mentions, in relation to the absence of any 
kind of tapetum in that genus, that ‘ physiologically its place is taken 
possibly by the basal part of the nucellus, the cells of which are densely 
packed with contents ’. He further adds that growth of the nucellus takes 
place mainly in this basal part. This also holds for both integument and 
nucellus in Podocarpus. 
