4 QUEENSLAND FOSSIL FLORAS 
points of view, viz.: that of the botanist and that of the 
geologist. 
From the purely botanical point of view only those 
remains in which structure is preserved are of value, and 
these are decidedly in the minority. Where conditions 
have been favourable, however, the preservation of 
structure is often very perfect, and the material exhibits 
detail of cell structure comparable with that of present-day 
plants. To illustrate this, it is sufficient to mention the 
completeness of our knowledge of the organisation of 
numerous extinct genera such as Calamites, Lepidodendron 
and Lyginopteris amongst Paleozoic forms and_ the 
Bennettitee from Mesozoic strata. The degree of 
preservation is often truly remarkable, amongst the most 
striking examples being (a) the flowers of the Mesozoic 
genus Cycadcoidea ; (b) leaves of Alethopteris and Neuropteris 
from the Carboniferous, in which the cell contents after 
treatment have taken up certain stains differentially ; 
and (c) the recognition of the embryo in numerous Paleozoic 
and Mesozoic seeds. 
These extinct forms throw considerable light on the 
problem of the evolution of the flora of to-day, and without 
a knowledge of them a satisfactory solution of this problem 
could hardly be expected. 
Geologically, plants are important for stratigraphical 
purposes, and it is very often useful to have distinctive 
names for plant remains which are of little value from a 
purely botanical point of view. Many botanists are apt 
to forget the value of fossil plant fragments in this 
connection, but provided the fragments represent a distinctive. 
and recognisable type, there is no doubt of their value to 
the geologist, whether they show detailed structure or not. 
Formerly, fossil plants were not relied on to any great 
extent in fixing stratigraphical horizons, and, as a result, 
there has been a tendency to regard them as being much 
inferior to fossil invertebrates for this purpose. The 
amount of paleobotanical work that has been carried out 
within the past two or three decades, however, has shown 
that plants are of very considerable value in fixing the age 
of beds in which they occur. 
