44 
THE FERNS OF SOUTH AFRICA 
But if fern study received a sound systematic foundation 
in Hooker and Baker’s Synopsis Filicum, already referred to, 
it has received further most valuable assistance in Carl 
Christensen’s Index Filicum (1906), which does the same for 
ferns as the Index Kewensis does for flowering plants. It is a 
most patient, industrious and accurate undertaking, investi- 
gating synonymy and priority of nomenclature in accordance 
with the laws of priority now adopted, and has been accepted 
as the authority for fern nomenclature (Brussels Congress, 
1910). 
The frequent changes of generic name may therefore be 
considered to have reached finality in so far as ancient record 
is concerned, and this brings us to the point where, in order 
to keep up with added information on distribution and to 
adopt the now recognised nomenclature, a second edition of 
the present work is called for. 
It is unfortunate that many of the generic names used in 
Hooker and Baker’s Synopsis Filicum , and from them used 
in the first edition of this work, have had to be set aside in 
favour of generic names now proved to have had priority 
of claim ; but as Christensen’s work is now in use in all 
leading herbaria it is advisable at once to use its nomencla- 
ture, even at the expense of using unfamiliar names instead 
of well-known ones now relegated to synonymy; and this 
has been done, with very few exceptions, in the present 
work. 
Christensen follows mostly the nomenclature and arrange- 
ment adopted in Engler und Prantl, Die natiirlichen Pflanzen- 
familien , but has also carefully studied Hooker and Baker’s 
Synopsis Filicum , 2nd ed., 1874, and Dr H. Christ’s Die 
Farnkrauter der Erde, 1897, an d has in most cases given the 
specific names used in all these three works, either as retained 
species or as synonyms. 
Christensen has further enhanced his work by the publi- 
cation of a Supplementum, 1906 — 1912 (1913), to his Index 
Filicmn , in which reference is made to several South African 
species. 
In Brause, Fedde Repert. 11. 1912, Hymenophyllum Mar- 
lothii is described. 
