

THE BRITISH FERNS. 
Genus VIII: SCOLOPENDRIUM, Smith. 
GEN. Cmar.—Sori indusiate, linear, often elongated, approximate 
in parallel and opposite pairs face to face; receptacles situated on 
the anterior and posterior sides of venules belonging to adjacent 
fascicles of veins. Indusium linear, plane, membranaceous, twin, 
each part opening on its exterior side with reference to the fascicle 
to which it belongs, so that the twin sorus opens along the centre. 
Veins forked from a central costa; venules direct, parallel, normally 
free, terminating within the margin in club-shaped apices. 
Fronds thick herbaceous, simple or pinnate, frequently and 
variously undulate lobate ramose multifid marginate cornute or 
lacerate, sometimes much depauperated. 
Caudex short, stoutish, erect or decumbent. 
The Scolopendrium or Hart's Tongue Fern, forms a sub-group of 
the Asplenieœ, in which the sori instead of being simple and distinct, 
are brought together in opposite pairs, so that what appears to be a 
line of spore-cases forming a sorus, is in fact a double line forming 
a double or twin sorus. This peculiarity of structure is not confined 
to the simple-fronded species inhabiting Great Britain, but occurs 
also in certain pinnately-divided exotic species, and may therefore 
be considered as of sufficient importance to be employed for the 
purpose of generic distinction. 
The veins in the genus Scolopendrium issue from the main rib or 
costa alternately, each one being once or twice divided near the base 
in a dichotomous manner, so as to form a tuft or fascicle of from two 
to fourlong parallel venules along the side of some of which the 
spore-cases are produced. It is not however to different venules of 
the same fascicle that the two parts of the twin sorus are attached, 
but to the exterior venules of contiguous fascicles. Thus the 
posterior venule of one tuft or group of veins, bears along its hinder 
side a simple sorus, and the anterior venule of the group next behind 

