i6 
European Ferns. 
HYMENOPHYLLUM. 
a^HIS is a large genus of ferns, including about eighty species of delicate plants, 
two only of which are found in Europe, the remainder being distributed 
through the temperate and tropical portions of the globe. They grow 
usually in moist places, upon rocks, or on the trunks of trees, often forming 
dense masses netted together by the branched thread-like rhizomes. They 
vary a good deal in size : some, such as H. parvifolium , a native of Moulmein, 
being minute plants, with stems only a line long, and tiny fronds scarcely 
more than twice that length ; others, as H. sericeuin, from tropical America, 
have long narrow fronds, which are sometimes as much as two feet long, 
although a foot is their more general size. The fronds are occasionally simple, 
as in the case of the very distinct H. cruentum , a Chilian plant with reddish 
fronds three or four inches long and an inch or more broad in their lower portion ; 
but they are more usually either simply or twice or thrice pinnatifid. About half the species 
are smooth and free from hairs, the remainder being more or less ciliated, or hairy upon the 
surface. Some beautiful species are in cultivation, such as H. sericeum already mentioned ; 
H. caudiciilatum , a Brazilian species with broad fronds, the ends of which are lengthened out 
into tail-like points ; LI. multifidum , from New Zealand and the islands of the Pacific, having 
finely-divided fronds about six inches long and nearly as broad ; and many more, chiefly from 
New Zealand and the West Indies. The Filmy Ferns are somewhat difficult to cultivate ; a 
very damp atmosphere is absolutely essential to them, and the amateur will find the Wardian 
case the most suitable treatment. Some succeed best upon logs of wood or tree-ferns, while 
others will grow well in a mixture of bog-moss and fibrous peat, with lumps of sandstone, 
the drainage being carefully attended to, as the water must not be allowed to stagnate. 
A very natural group (the Hymenophyllece) is formed by the two genera Hymenophyllum 
and Trichomanes, the species resembling each other greatly in form and habit, as well as in 
the pellucid membranous texture of the fronds. They are technically distinguished from all 
other ferns by the sori being borne at the margin instead of at the back of the fronds, 
the spore-cases being contained in deep urn-shaped cavities, and clustered round hair-like 
receptacles, which are the ends of the veins of the fronds. In Hymenophyllum the indusium is 
more or less deeply two-lipped or two-valved, while in Trichomanes it is entire; and this 
constitutes one principal technical difference between the two genera, the other being that 
the receptacles in Hymenophyllum are short, and included within the indusium ; while in 
Trichomanes they are continued beyond it, being often elongated and filiform, or bristle-like, 
in appearance. 
HYMENOPHYLLUM TUNBRIDGENSF, Linn. 
This and the next species are the smallest of our British ferns, and from their incon- 
spicuous olive-green hue and insignificant size, are frequently overlooked. They grow in dense 
masses, the slender black wiry filiform creeping rhizomes forming a matted network, from which 
arise the short membranous fronds. In the present species these are about one and a half to 
three inches long, and have a delicate cylindrical stipes ; they are ovate-lanceolate in outline, 
acuminate, deeply pinnatisect, a narrow wing of membrane connecting the pinnae into one 
