SUB-SECTION LASTREA. 
145 
THE BROAD BUCKLER FERN. 
N EPHRODIUM SPINULOSUM. — Desvaux. 
Fig. 42. — Nephrodium spinulosum, pinna (showing fructification). 
A WORD or two is requisite in order to point out why the ferns 
known as Lastrea dilatata and L. aemula are included in the 
present fern. 
There can be no doubt that locality, especially height above the 
sea, changes the character of a plant. We may instance “ the 
common Brake,” which attains 12 feet in height on Longridge 
Fell, and yet only 4 inches near the summit of Hellvelyn. As a 
rule, ferns are diminutive on mountains. In a wood at Hack- 
ness, near Scarborough (I am speaking of twenty years ago), N. 
dilatatum (Section 7) was near the base of the hill 5 feet high, and 
was common to half-way up this hill, where N. aemulum (Section a) 
mingled with it ; higher, aemulum was common and dilatatum 
absent. My brother and myself being surprised at this change, 
we determined to test it ; and from many thousand plants of 
aemulum we removed 500 to Highfield House. In a couple of 
years, several changed to dilatatum ; the next year an increased 
number, until at length aemulum was the exception to the rule. At 
the same time we had a score in pots, but none of these changed. 
The same has occurred with the mountain form alpinum, dwarf 
plants on removal having much increased in size. The Oak fern, 
only an inch high, and the Beech fern, not much larger, when 
gathered at the summit of Ben Lawers, assumed their natural 
size in three or four years. Polypodium vulgare, var. cambricum, 
and Scolopendrium vulgare, var. crispum, when planted in a wood, 
gradually reverted to the normal form of the species, whilst 
divisions of the same plants grown in pans did not change ; and, 
again, divisions taken from those planted out and repotted did 
in the course of time resume their original character of cambricum 
K 
