vi PREFACE. 
circumstance that in the Gnetacee the character of “ nakedness of 
the ovule’’ is manifest, admits the formal retention of the order in 
the Gymnosperme, and allows the accordance to it, in our ordinal 
conspectus, of a serial position which conforms with the practice 
adopted in other floras of the series in which the “ Flora of Tropical 
Africa ” finds a place. In the definition of the Gnetales, prepared 
for this conspectus by Dr. Stapf, due allowance is, however, made for 
the peculiar and ambiguous position of the class. The terminology 
employed in describing the organs of reproduction is intended to 
reflect our belief that, in spite of the nakedness of the ovule, the 
affinities of the Gnetales are with the angiospermous rather than with 
the gymnospermous phylum. 
Associated with this difficulty as to the nine of the Gnetales 
is the more serious one created by the modern view as to the relation- 
ship which these two great phyla bear to each other. The phe- 
nomenon of gymnospermy, first pointed out by R. Brown in 1826, 
was turned to taxonomic account by Brongniart as early as 1828. 
But when Brongniart recognised in the Gymnosperme a distinct 
natural group, he regarded that group as an integral part of the 
Dicotyledones. Tt was not until 1864 that A. Braun proposed the 
treatment of the Gymnosperme as a division of the Phanerogame 
equal in status to the Dicotyledones and the Monocotyledones taken 
in conjunction. The evidence in favour of the view, adopted by 
Hooker in 1876, that the two primary phanerogamous divisions, 
Angiospermae and Gymnosperme, represent quite distinct lines of 
evolution, is so strong that this disposition is now generally accepted. 
The series of Colonial Floras was initiated in 1859, and the first 
work in this series was issued in 1861, while the view expressed by 
Brongniart in 1828 was still generally accepted. In that flora the 
Gymnosperme were accordingly regarded as a subclass of the Dicoty- 
ledones, and were assigned a serial position immediately after the 
really dicotyledonous subclasses and immediately before the mono- 
cotyledonous ones. The view that the Gymnosperme are a subclass 
of the Dicotyledones has not been maintained in every Colonial 
Flora completed since 1861. In one instance the Gymnosperme 
have been regarded as a group, within the Dicotyledones, equal in 
status to the whole of the angiospermous subclasses of that class. 
In other cases the Gymnosperme have been advanced to the rank 
of a distinct class, comparable in status with the Monocotyledones 
on the one hand, the Dicotyledones on the other. Neither of these 
two modifications of the original view necessitates a change in the 
