10 
INTRODUCTION. 
still more evidently than even in the preceding order, as the receptacle is in the 
place of a lobe of the leaf. The laminae of the lobe contracted form the valves of 
the receptacle, and its vein or nerve exists as a central column, covered with 
fructification ; in Hymenophyllum terminated thereby ; in Trichomanes the vein 
is prolonged much beyond the thecae. The root of Trichomanes is thick, black, 
and very hairy ; that of Hymenophyllum very long, creeping, and matted 
together. 
DISTRIBUTION. — “ Hymenophyllaceae, more impatient of drought than 
many of the Polypodiaceae, delight in shaded situations, where they are bedewed 
by frequent mists and the spray of waterfalls ; growing on damp rocks and stones, 
half buried amongst the Mosses that accompany them ; and like the Mosses 
rapidly shrinking or expanding with variations of moisture. Two of the three 
native species are rare in Britain, especially the Trichomanes, which is peculiar to 
Yorkshire, if it be not now extinct in England. Another, Hymenophyllum Tun- 
bridgense, is found in various counties of England and Scotland, varying from 
Devon and Sussex to the river Clyde in Scotland. The much more abundant 
H. Wilsoni, was so long confounded with the former species, that it has been 
supposed a rarer plant than it really is, for the greater number of localities 
assigned for H. Tunbridgense belong to H. Wilsoni. This latter species ranges 
from Cornwall, northward, to Sutherland, and rises on the mountains of Wales 
nearly to 2000 feet, and not improbably more.” — Mr. Watson’s MS. 
OSMUNDACE/E. 
( Contains only the genus Osmumla.) 
Osmund ace/e, fir., Kaulf., Lind., Hook., Agard. 
Osmunde/I!, Spreng. 
SCHISMATOPTERIDES, Willd. 
SPURU.E Gyratve, Swz. 
Rim at.e, Mohr. 
Acrogyrat.e, 11 ernh . 
Exannuuat/E of Modern Authors. 
STRUCTURE. — This order varies very little from the two former, except 
in the fructification. The rachis is similar in vernation and structure — the mixed 
vessels are arranged in the indigenous species in part of a circle like the letter ©. 
The cuticle of the stem is void of stomata, but on the under surface of the 
foliaceous part of the frond they are round, abundant, and very large. In the 
fruit, a great difference exists between this and the Annulate Ferns. The theca; 
are transparent and wrinkled, but not ringed ; they are not torn asunder 
irregularly, but open at a distinct longitudinal fissure, and are thus shown to be 
regularly two-valved. They are not fixed at the back of a leafy frond, but 
densely clustered at the top into a large erect raceme. The leaflets of the upper 
part of the frond are also seen partly changed into thecae of similar character, 
thus proving the origin of the whole. (See Osmunda.) 
