150 The Plant Formations. 
the species must have been markedly altered, while each burning would cause 
a rearrangement. Especially is this the case in the N., where, as may readily 
be seen, a series of fires transforms shrub-heath into fern-heath, for a time, at 
any rate. Bearing the above in mind, who can say that even so common a 
plant as Pomaderris phylicaefolia was not comparatively rare in primitive New 
‚Zealand? & RER | 
Shrub-heath is of varied origin. It may be a natural replacer of rain-forest, 
. a succession-stage after moor or after river-bed, or a new-comer after the forest 
is destroyed by man. Between the natural and the artificial it is now, in most 
cases, impossible to discriminate. | Be 
The dominant ecological character of the association is the prevalence of 
the ericoid-form amongst its members, 17 species of woody plants possessing 
it to a marked degree. The number of tubeious-rooted orchids is a rather 
striking feature, but they give no distinctive mark to the vegetation. 
2. Gumlands’ Heath. 
Modified though this is by man, it contains as a rule ‘) few introduced 
plants and is a clearly-defined and striking association. It covers much of those 
deep, clay soils that form so large a part of the surface of the Northern 
province. At one time kauri forest. occupied this ground as evidenced byte 
abundance of fossil resin and even undecayed logs beneath the surface. The 
clay varies in colour from brick-red, by way of orange and yellow, to almost 
white, this latter being especially barren. In winter it becomes saturated with 
water, but, in summer, baked by the sun, it is extremely dry and opens out 
‚into many cracks. Hollows and low-Iying ground are always filled with peaty 
water or at least remain permanently wet providing where wettest bog-conditions; 
here their vegetation is treated as moor. . 
The species number about 81, the following of which, absent in southern 
‘ heaths, are more or less common in this association: — Lycopodium densum, 
Z. cernuum, Phylloglossum Drummondii, Paspalum scrobiculatum, Schoenus 
tendo, Lepidosperma laterale, Cordyline pumilio, Thelymitra pulchella, Persoonia h 
nmannia sylvicola, Carmichaeli tralis, Pomaderris. 
_ Ppine-like Lycopodium densum, or they may grow separately. Probably there 
will also be some Pieridium, Pomaderris phylicaefolia and Styphelia fasciculata. 
