















142 THE BRITISH FERNS. 
sium also double, narrow, entire, the two membranes belonging to 
the two lines of spore-cases set face to face, at first conniving 
or overlapping each other, but at length separating and becoming 
finally pushed back in opposite directions and hidden by the crowded 
mass of spore-cases. Spore-cases numerous, obovate, reddish-brown. 
Spores roundish or oblong, muriculate. 
Duration. The caudex is perenrial. The fronds are persistent, 
the first young ones being produced about April, and others later in 
the year, all remaining until long after fresh ones are produced to 
succeed them ; the plant is therefore strictly evergreen. 
The common Hart’s-Tongue in its normal state is at once known 
from all other British Ferns by its long strap-shaped succulent-look- 
ing deep-green fronds ; and technically by its linear twin sori; and 
many of its varieties retain sufficient of its general aspect to enable 
those who are at all acquainted with the British Ferns to recognise 
at a glance their relationship to the specific type. But the varieties _ 
are almost endless, and sometimes so completely lose all resemblance 
to the common state of the plant that a tyro might well be excused 
for want of faith in their specific identity. Nevertheless some of 
the most remarkable of these have been artificially produced from 
other aberrant forms in which the relationship was still evident, and 
they remain in the hands of the cultivator as monuments of that 
plastic force in nature which gives origin to new forms of vegetable 
life, some of which doubtless become permanent, overcoming the 
accidents and the chances of the conditions which surround them, 
and destined eventually to be recognised as distinct, their origin 
being often unsuspected. Those of these unnumbered forms which 
we have thought deserving of botanical recognition are to be consi- 
dered rather as types of variation than as individual forms, most of 
them comprising a series of analogous subvarieties. 
This beautiful sylvestral species is generally dispersed over the 
United Kingdom ; affording, as Mr. Watson remarks, a very decided 
example of a prevalent condition of distribution which may be 
traced in the greater number of British plants, namely, a tendency 
to linger along the coast line to a higher northern latitude than that 

