5o ON GENERA AND SPECIES. 
ing sixty-four plates, the drawings of the latter as well as 
part of the preceding being derived from living plants of 
the Kew collection. The practical use of these works is 
iu assisting to determine species, and which, either under 
the same name or as synonyms, will be found in his last and 
great work the “Species Filicum,” the most important 
systematic work on Ferns yet published, being a description 
of all known Ferns, particularly of such as exist in the 
author’s herbarium (previously noticed), and such as are 
with sufficient accuracy described and figured in the works 
of other authors. It consists of five volumes, the first of 
which appeared in 1846, and the fifth in 1864, its prepara- 
tion having occupied his leisure time for a period of not 
less tban twenty years. It treats of the orders Gleicheni- 
acee and Polypodiacew only, of which 2,401 species are 
described, with their synonyms, which amount to about 
4,300, as also their native countries and names of collectors, 
ilustrated with 300 plates representing 522 species. He 
} arranges the whole under sixty-three genera, fourteen 
. Of which contain only one species each, thus present- 
| ing a great contrast to the mass of species which he 
. continues to retain under the characters assigned by Lin- 
nus and Swartz, to such genera as Polypodium, Aspidium, 
Pieris, and Acrostichum, thus avowing his preference for 
large genera by strictly adopting the characters derived 
solely from the fructification. With regard to which he 
. says, “Increased study has, he must confess, strengthened 
. his conviction that those. botanists who have shown them 
qe peculiarly addicted to multiplying genera have no 
always taken nature as their guide, nor succeeded i 
| eliciting a simple nor tangible arrangement, yet have their 
. close and accurate investigations thrown a new light on the 
study of Ferns, a light which cannot fail to Se, the re 
