Growth-Forms. 111 
species the bases of the trunk may be more or less swollen or buttressed. 
True plank-buttresses, 1.8 m high by ı2.5 cm thick, occur in Zaurelia novae- 
zealandiae and more rounded ones in Beilschmiedia tawa and Podocarpus 
dacrydioides. In the tall and medium-sized trees the trunk is frequently un- 
branched for about °/, of the height of the tree. In the greater part of the 
species the bark is thin, but bark ı2 mm or more thick occurs in some species 
(Agathis, spp. of Podocarpus &c.). 
The degree of density and of spread of the tree-crowns is largely a matter 
of environment. very considerable proportion are dense and rounded while 
but few have really far-spreading branches. Podocarpus dacrydioides has a 
very sparse, narrow crown, small out of all proportion to the size of the tree. 
Knightia excelsa is almost as fastigiate as the Lombardy poplar and it shows 
up distinct from the general forest-mass. The head of Metrosideros robusta, 
though rounded and somewhat wide-spreading, is not dense owing to the leafy 
portion of each branch not intermingling. 
The roots of the trees rarely descend deeply but spread out horizontally 
for a great distance and the uppermost, in some species, are only half-buried 
or, at times, raised above the ground-surface. Nodules are abundant on the 
roots of the Pinaceae, Taxaceae and Leguminosae. Rhopalostylis gives off 
short reddish stilt-roots at 30o cm or more from the base of the trunk. The 
tree ferns have a mantle of aerial roots surrounding their trunks. The base 
of the trunk may thus be much swollen, e.g. in Cyathea dealbata the base 3 
may measure 46 cm in diam. while it is not until a height of 56 cm from the #: 
ground is reached that the trunk is of the general diameter of ı5 cm. In leaning 
trunks of the above fern large wedge-shaped masses of aerial roots en 
jut out from the under-surface. “ 
The leaves of the trees are: — Simple 56, 20, broad 65, narrow 8, In 
cupressoid 3, glabrous 64, more or less hairy ı2 of © 
and waxy beneath'7. Their dimensions are: — - Very small (25 cm and less 
in length) ı1; small (2.5 em to Ser) u medium cm) 30; I 
(to cm to 20cm) ı2 and 20cm. ards) 
"include the palm and the tree-ferns, the leaves of which frequently 
2m in length and in the case of Cyathea medullaris may reach 6 m 
by 1.5 m broad. As for the texture of the leaves those 
are thin and of 46 1 more or less thick and coriaceous. ” 
