TERTIARY PROTEACEAE 
27 
Fig. 2 A, drawing of holotype of Banksieaephyllum 
urniforme, NMV P15127, see Fig. 1 A; scale = 2 mm. 
B, drawing of specimen of B. fastigatum shown in 
Fig. IE, NMV PI5128); scale = 2 mm. 
response to low nutrient levels in the soil, par¬ 
ticularly low phosphorus (Beadle 1966). There 
has often been confusion about the interaction 
of nutrient levels and climate (in particular low 
rainfall) as contributing factors to sclerophylly. 
Many sclerophyllous characters are also useful 
xeromorphic adaptations (e.g. small leaf size, 
thick cuticle), and with features such as these it is 
difficult if not impossible to determine whether 
low nutrients or a dry climate was the causal 
factor. There are some leaf characters, however, 
which can be described as xeromorphic and are 
distinct from scleromorphy. Most prominent 
amongst these are adaptations directed towards 
protecting the stomates, so that the boundary 
layer resistance is increased (e.g. sunken 
stomates, stomates in pits, revolute leaf margins, 
hairs around the stomates, etc.). It is the pre¬ 
sence or absence of these characters which 
should allow an interpretation of the factor(s) 
most affecting leaf form in Banksieaephyllum 
(Hill in press). 
Although all species of Banksieaephyllum de¬ 
scribed from the Latrobe Valley coal are scle¬ 
rophyllous, only some have adaptations which 
can be considered as solely xeromorphic. B. 
angustum and B. acuminatum are the most xero¬ 
morphic species, having strongly recurved leaf 
margins, stomata sunken in pits, and very hairy 
stomatal leaf surfaces. Blackburn (1985) noted 
these xeromorphic features and their relation¬ 
ship to the darker coals which accumulated in 
the drier environments. Some of the other spe¬ 
cies (e.g. B. laeve, B. obovatum) exhibit almost 
no xeromorphic adaptations, and the remaining 
species are intermediate in form. Even the most 
xeromorphic species are not as strongly adapted 
to preventing water loss as are some of the extant 
Banksia and Dryandra species, and they may be 
in a transitional state towards this development. 
Thus it can be concluded that these fossils offer 
the earliest fossil evidence of xeromorphy in 
Australia, even though Banksieaephyllum is 
recorded from the Palaeocene onwards. This 
suggests that these coal floras are an important 
site for the study of the way in which the mor¬ 
phological adaptations to the Mediterranean cli¬ 
mate evolved in Australia. Future studies on 
other taxonomic groups should refine these con¬ 
clusions. 
ACKNOWLEDGEMENTS 
This study was supported by grants from the 
Australian Research Grants Committee and the 
Ian Potter Foundation. I thank Tom Rich and 
