THE BRACKEN 
189 
shaped pinnules broadest at their bases, and attached to the 
pinnae by short stems. The pinnules nearest to the main 
rachis are again divided, in luxuriant specimens, into oblong 
blunt-pointed lobes, which, however, towards the apices of the 
pinnules, are merged into the substance of the latter. The 
fronds, pinnae, and pinnules are always less divided towards 
their apices than at their bases. One curious and charac- 
teristic exception to this must however be noted. On each 
pinna the pair of pinnules nearest the main rachis of the 
frond is generally dwarfed — the pinnule on the upper side of 
the mid-rib of the pinna being the smaller of the pair, so 
small sometimes as to consist merely of an undivided blunt- 
pointed leaflet — and sometimes absent. Small and stunted 
specimens of Bracken are often only twice pinnate, and 
in such cases the pinnules, instead of being divided into 
distinct and separate lobes, are merely what is called 
pinnatifid, or deeply cleft, the lobes being run together 
■at their bases. Along on each side of the mid-veins of 
the lobes are alternate veinlets, which are sometimes once 
and sometimes twice forked as they run to the margins 
of the lobes. It is along these lobe margins that the 
fructification of the Bracken is produced in lines, the in- 
dusia or coverings of the spore cases being formed by a 
rolling back of the bleached edges of the lobes. When the 
spores are ripe the under side of the Bracken has a very 
beautiful appearance, the rust-coloured marginal lines of 
spore cases meeting at the lobe points in the form of angles, 
and finely contrasting with the dark-green colour of the rest 
of the frond. From the normal form, which has just been 
described, of the Bracken, there are in these Islands about 
eight or ten departures or varieties. But this is the only 
species which we possess of the genus Pterin, which consists 
of Ferns whose sporangia are arranged in continuous lines 
on the under edges of the lobes of the fronds, and covered by 
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