XXXVI 
European Ferns. 
were added, and the number has since been very materially increased by the exertions of 
recent collectors. Of course the view of species taken in the “ Synopsis ” is a very broad one, 
many forms which are regarded as distinct by other writers upon ferns being considered as varieties 
or synonyms of other species by Hooker and Baker — not always without a protest from those 
whose knowledge of the plants is derived rather from growing examples than herbarium 
specimens. Thus the veteran pteriologist, Mr. John Smith, speaking of Mr. Baker’s important 
memoir on the ferns of Brazil, published as part of the “Flora Brasiliensis ” in 1870, says: 
“ On taking into consideration the extensive territory of Brazil, with its various climates 
favourable to the growth of ferns, from those growing at elevations that may be termed sub- 
arctic to others luxuriating in the lower hot valleys and rocky or forest ravines, the number 
of three hundred and eighty species [Mr. Baker enumerates three hundred and eighty-seven 
as Brazilian] may be considered small ; but here again comes the question, What is a species ? 
and judging from Mr. Baker’s view, it would appear that many plants, originally described as 
species, which successive authors have acknowledged to be distinct, are, nevertheless, in many cases 
regarded as synonyms ; thus ferns long accepted by previous pteriologists cease to be so. When 
I say long accepted, I go upon the evidence of Link, Kunze, Schott, Mettenius, and myself, 
who have had for many years under their observation living examples of species all well 
recognised as being different from one another in some important characters seen only in the 
living state ; but Mr. Baker, with herbarium specimens, makes no scruple of lumping many of 
such under one specific name. For instance, under Polypodium lycopodioides there are no less 
than twenty-two synonyms, and under P. brasiliensis eighteen.”* If we want an illustration 
of the widely differing views as to the limits of species, we may find it in the genera 
Hymenopkyllurn and Trichomancs. Dr. Van den Bosch, treating of the Hymenophyllcce of Javaf 
alone, makes no less than twenty-four genera out of the two just named, under which he 
describes four hundred and fifty species ; while, on the other hand, Hooker and Baker, in the 
“Synopsis Filicum ” (1868), admit only a hundred and forty-nine species of these two genera 
as existing in the whole world. It must be allowed that botanists who take their descriptions 
from dried and often fragmentary specimens of plants have a natural tendency to the multi- 
plication of species ; this often, however, produces a reaction which leads to an opposite 
extreme, an over-caution against too low an estimate of what is required to constitute a 
species. There can be little doubt but that errors on both sides are frequent enough, especially 
among certain groups of flowering plants. The roses and brambles, for instance, afford a good 
illustration of what is termed in scientific slang “ splitting,” our common dog-rose {Rosa caninci) 
being divided by “critical” botanists into very numerous species, while those into which our 
common blackberry (Rubus fruticosus ) has been “split up” may be reckoned by hundreds. 
As in most other matters, a middle course is probably safest — and it is the one which we 
have adopted in the present work ; we have not, for example, been able to follow Hooker and 
Baker in uniting the two Filmy Ferns {Hymenophyllum tunbridgense and H. Wilsoni) under one 
species, nor have we placed together the Oak Polypody (. Polypodiitm Dryopteris) and the 
Limestone Polypody (P. Robertianum). Although most writers on ferns would consider that 
Mr. Smith had too great a tendency to multiply genera, there is much force in his remark as 
to the differences between certain species being readily recognisable in living examples, 
although less apparent in herbarium specimens. Lvery practical field botanist is aware that 
there are certain points connected with the habit, mode of growth, and general appearance 
of some species of flowering plants which are at once observable in the field, although they 
• “ Historia Filicum,” pp. 59, 60. f “ Hymenopliyllaceae Javanicae.” 
