256 UNDERWOOD: REVIEW OF THE GENERA OF FERNS 
always unfortunate, they are our inheritance from the lack of sys- 
tem of the past generations of botanists, and can never be ration- 
ally used in an argument where principles of nomenclature only 
are involved.* In this case many of the species have already been 
placed pct the genus AAyriwm which appears to be the next 
in line. 
10. PorxropiUM (1082) as a genus took its origin from Tour- 
nefort (Inst. 540. A. 376), tho the name had been used by Theo- 
phrastus, and is based on P. vulgare, the common European spe- 
cies. Linnaeus (Gen. Pl. 1737) included Louchitis Tourn. (Poly- 
stichum Lonchitis Roth) in the genus. In Hort. Cliff. 474 P. vulgare 
is the fourth species mentioned. In Species Plantarum 58 species (of 
which over 60 per cent. are American) are included, of which P. 
lanceolatum(§ Phymatodes) is the first named and the genus includes 
species of "ALegopteris, Polystichum, Dryopteris, Filix, Cyathea and 
other modern genera. 
II. ADIANTUM (1094) also takes its origin from Tournefort 
(Inst. 543, A. 377), tho the name had been used by Dioscorides, 
and is naturally based on the common European species A. capil- 
Jus- Veneris. Linnaeus (Gen. Pl. 322. 1737), quotes Tournefort, and 
in Hort. Cliff. 473 includes four West Indian and Bermuda species. 
In Species Plantarum 15 species are included, two-thirds of which 
are American; as in all his fern genera the simple species are 
first described, A. reniforme of Madeira is naturally the first named. 
12. TRICHOMANES (1097) was established by Linnaeus (Cor. 
Gen. Pl. 20. 1737, and Hort. Cliff. 476), as a monotypic genus based 
on Plumier's plate 86 which is Trichomanes crispum. The original 
Trichomanes of Tourn. (Inst. 539. pl. 375. 1700) was Asplenium 
Trichamanzs as recognized by Linnaeus when he established the 
latter genus. In Species Plantarum, Linnaeus gives eleven species 
of Trichomanes, of which six are American, but includes besides 
filmy ferns of the genus Hymenophyllum, certain thin leaved species 
of Davallia ; the first species mentioned is T. membranacum, also 
a true Trichomanes, but T. crispum is clearly the legitimate type of 
the Linnaean genus. 
* Unfortunately one of the first tions that arises in- o minds.i in nnde ae 
any question of nomenclature is not ** ‘Is the principl one’ 
** How much change will it Ade " . So long as dis: mental cae is rampant a. 
stable rational system is practically impossible. 
