XIII ITEHIS. 
191 
what velvety externally, often forming thickly interwoven 
usually horizontal masses just beneath the surface of the 
soil. The fronds, which are lateral and adherent, and 
produced singly at intervals along the caudex, are of 
annual duration ; the young ones grow up in May, and 
being extremely succulent and tender, are often killed 
by late frosts ; they become mature by the latter end of 
July, and are invariably killed early by the autumnal 
frosts, then becoming of a reddish brown colour, but from 
their rigid texture, maintaining for some time their form 
and position. When they first grow 
up the tops are bent down against the 
stipes, from which position they rise and 
expand gradually. They are very 
variable in size, from six to eighteen 
inches on poor soil, and parched situa- 
tions, to three or even eight and ten 
feet in rich soil and sheltered localities. 
Their form also varies the smaller 
states being usually somewhat trian- 
gular, and the larger much more elon- ' 
gated. The stipes is rather over half 
the length of the frond, and is green, 
somewhat pubescent when young, and 
when mature angular with sharp edges 
which inflict severe wounds if the plants 
are incautiously pulled ; the part under 
ground is black, velvety, and spindle- 
shaped. A transverse section of the 
stipes presents the ends of the vascular bundles arranged 
in a figure which is by some thought to resemble the im- 
perial eagle, whence the specific name. 
The composition of vigorous fronds is thrice pinnate. 
Sometimes, when grown in exposed situations, the first 
pair of pinna? are unusually enlarged, giving to the frond 
a kind of tripartite-appearance; but under other con- 
ditions, the primary rachis becomes extended, throwing 
