106 BRITISH FERNS, 
but sharp and distinct spines; each tooth, with its 
accompanying spine, has a decided curvature towards 
the apex of the pinnule. The veins of the pinnules 
are alternately branched, each system of branches 
entering a division of the pinnule, and the anterior 
branch bearing a circular mass of seeds just within 
the notch which occurs between each two divisions: 
this mass is covered by a flat, reniform involucre, 
the margins of which are waved, entire and without 
_ glands, a character which, as far as my observation 
has extended, is constant, and is of great importance 
in distinguishing the present plant. Owing to the 
constant position of the clusters on each pinnule, they 
form a regular double line, the midyein of the pinnule 
passing up the centre; but when the pinnule is com- 
pletely divided into lobes each branch of the vein 
usually bears a mass of seeds: this is more fre: 
quently the case in those pinnules which are nearest 
the main stalk of the frond; and it may be observed 
