VIII 
[^ explanation of the principles I have adopted in preparing the Index 
only a few words are needed, as everybody using the book will soon be able 
to understand the plan of it. 1I shall here confine myself to following: — 
As a basis of the whole work I have chosen the system followed in ENGLER 
und PRANTL: »Die natürlichen Pflanzenfamilien-; still I have found it cor- 
rect to depart from this system in some few cases, which are all emphasized 
in the first part of the Index, partly from systematic and partly from nomen- 
claturic reasons. Although I am far from agreeing with DIELS in his view of 
genera, still I have considered it right upon the whole to follow his system, 
because Engler und Prantl certainly is or will be the basis of the arrangement 
of species in many museums and private collections. Only in a very few cases 
(for instance by adopting Lepicgstis as a separate genus) I have not thought 
it fit to follow DIELS. In other cases the deviations are owing to later in- 
vestigations, to which I everywhere have paid the greatest attention. 
. Besides stating where the original description isto be found, I have under 
each species quoted the page, where the species is described or mentioned in 
HOOKER and BAKER: »Synopsis Filicum«, 2. Ed. 1874 (abbreviated to HB), 
in H. CHRIST: »Die Farnkráuter der Erde:. 1897. (Chr.), and in »Die Natür- 
lichen Pflanzenfamilien- Teil 1, Abt. 4. 1899— 1902. (NPfl. These quotations 
will, I think, be of considerable value, as you generally in works easy of ac- 
cess quickly may find the desired information about a species without being 
obliged to resort to the original diagnosis, which often is so difficult to get at. 
Besides, in genera monographically dealt with in recent times, the monograph 
in question is quoted as much abridged. 
With regard to the limitation of species I have, of course, in most cases. 
had to follow others. My principle has been: In genera, treated monographi- 
cally, I have chiefly followed the monograph concerned; otherwise I have relied 
on the identifications of authors having had the original specimens for exami- 
nation, or others, who to a great extent have been enabled to study the spe- 
cies in the field (for inst. JENMAN as far as the West-Indian, and BEDDOME 
as far as the Indian species are concerned). Still I have no doubt that a great 
number of names, reduced to synonyms, are representing good species, and 
especially many forms by HOOKER and BAKER reduced to mere synonyms, - 
according to their comprehensive ideas of species, probably will prove to be 
good species. The numerous species described as new these last years have, | 
of course, been adopted without criticism. 
MS. names ! have not included. An exceedingly great number of these . 
are given as synonyms in different pteridographical works. They have no 
claim of priority as published names. and the authors are doing the nomen- . 
clature a bad service by reprinting such names without descriptions. À con- 
tinuation of this practise ought to be carefully avoided in the future. If 1 — 
were to include these MS. names, which is done in several Indices, my book 
would have been larger by several sheets. Names of garden forms are rather 
fully included only from the time of the last ^0 years, of older forms only 
such as are still being cultivated. 
I must point out that not all the synonyms of a species are given under 
the species; I have preferably only referred to thosc representing forms, which. 
are often considered as being valid species and without exception forms that 
are being dealt with as species in one of the three mentioned principal works, 
In addition I have everywhere of each species as wcll as of each of its syno- - E 
nyms named as far as it was possible all the genera, to which each form has - 
been referred, by whom and when, in chrono'cgieal order. This should give ^ 
