306 Brooks and Stiles .— The Structure of 
found on mountain ranges at a considerable elevation. Just as Pinus may 
be considered the dominant Coniferous genus of the Northern Hemisphere, 
so Podocarpus occupies a similar position among the Conifers of the 
Southern regions. 
In regard to the distribution of the genus in geological times, most 
of the specimens referred to Podocarpus or closely allied genera have been 
determined from leaves only, and it is well known that leaf determinations 
are frequently untrustworthy. In this connexion mention may be made 
of the striking similarity in external features between the leaves of some 
species of Agathis and those of the Nageia section of Podocarpus . Seward 
and Ford ( 16 ) found, on cutting sections of a species originally referred to 
Dammar a Motleyi , that the plant so named is really a species of Podocarpus. 
Assuming that some at least of the specimens are correctly deter¬ 
mined, then Podocarpus , like Araucaria, must have been widely distributed 
in the North temperate zone during the later Mesozoic and Tertiary times. 
Pilger states that the leaves from the Potomac or later Mesozoic flora of 
the United States are to be referred to the Nageia section of the genus on 
account of the plurinerved form of venation, while leaves from the Eocene 
and Miocene strata of Europe belong to the uninerved sections of the genus. 
Podocarpus shows a considerable range of habit among its many 
species. Several of them are large trees ; e. g. P. amarus attains a height 
of sixty metres in Java, and P. dacrydioides forms practically pure forests 
in New Zealand. On the other hand, P. alpinus , found on mountains in 
Tasmania, is a low shrub, and P. nivalis , on exposed places in the alpine 
regions of New Zealand, becomes a dwarf shrub with prostrate branches. 
Vegetative Organs. 
Stem. 
The structure of the wood of P. spimdosus is very similar to that of 
P. macrophyllus described by Penhallow. Resin canals are absent in the 
wood, but there is a ring of them present outside the phloem. Their place 
in the wood is taken by resin cells, which are present in considerable 
numbers. The bordered pits of the secondary tracheides are uniseriate; 
no trace of the Araucarian type of pitting could be discerned, such as has 
been described by Gothan (8) for Dacrydium spp. and for Saxegothaea by 
Beust ( 3 ), Gothan (8), and Stiles ( 17 ). The medullary rays are invariably 
uniseriate, and are from one to three cells deep. The cells of the rays 
contiguous to the pith frequently contain resinous material, but apart from 
this all the cells of the rays are alike, there being no tracheidal cells such 
as are met with in the rays of Pinus and some other Conifers. There is 
a small central pith which consists mainly of resin cells and groups of stone 
cells; the latter are very conspicuous. Resin cells are also extremely 
abundant in the cortex. 
