o o ON GENERA AND SPECIES, 
able number of new species, many of which appear to be - 
founded on very imperfect, and not well.authenticated à 
materials. A few of his new genera are admissible and ` 
wil be noticed in their respective places; the greater 
number, however, are untenable ; for instance, he describes 
about fifty species of the genus Blechnum, of authors, which 
he arranges under five genera, namely, Blechnum, Parablech- 
num, Distazia, Mesothema, and Blechnopsis; the differential 4 
character of these genera is, however, so slight that Ido - 
not consider them worthy of adoption (see Blechnum). m 
Another instance of creating genera on what may be - 
called fancied differences, is the genus Niphobolus of Kaul- 
fass, of which Presl enumerates thirty-nine species arranged _ 
under eight genera. On examining numerous sets of herb- _ 
arium Specimens said to be species of this genus, I find the © 
intermediate forms are so numerous that it is impossible to 
collate them, so as to arrive at any satisfactory conclusion 
as to what number of them are distinct species, for with all. 
. . the evidence that has come before me, I have not been able 
. . to define more than about a third of the species recorded 
by Presl, all of which I continue to retain under Niphobolus. 
TR Many other of Presl’s genera have as little title to rank 
às such as those of Blechnum and Niphobolus, and I deem it 
best not even to notice them as synonyms, as it would only 
add to the already overburdened Fern nomenclature. 
In the preface to this book it is shown that it is now | 
_ tmore than fifty years since the writer commenced to study 
: the collection of Ferns in the Royal Botanic Garden at ` 
.. Kew, then amounting to about forty exotic species; and 
-~ having had the opportunity of profiting by the verbal 
. Observations of Robert Brown, who often directed my 
attention to the mode of the arrangement of the veins 
. in different species of the genus Polypodiwm, as forming 
