124 THE ESSEX NATURALIST.
stay in the West of England, he was fascinated with and collected
all the different shapes of ivy leaves he could find; the plant
does not grow wild in America.
HETEROPHYLLY ASSOCIATED WITH REDUCED
LEAVES.
The common Barberry, Berberis vulgaris, has the leaves of
the mature branches reduced to a stiff three-branched spine,
or, on weak branches, to a single spine, while the typical oval
foliage-leaves, with delicately spinose margin, are formed on
axillary shoots. After a bush has been cut hard back the
well-fed suckers springing from the stump bear first well-
developed strongly spinose leaves; the later leaves are suc-
cessively more reduced and leathery and more spinose, until
they are simply spines, with leafy shoots in their axils.
Another example of abundant nutrition associated with strong
growth is seen in the more leafy stipules of summer shoots of
Hawthorn and Plane. In spring the Plane stipules are in-
conspicuous; in early autumn, if some branches have been cut
back, on newly formed shoots broad leafy stipules with a sheathing
base are developed, surrounding the shoot above the leaf base.
Finally I may refer to the
HETEROPHYLLY MET WITH CHIEFLY UNDER
CULTIVATION,
in the many cut-leaved varieties of some of our common trees,
such as those of the lime, beech, and alder; also to the beautiful
crested "sports" of many species of fern, selected and prized
by fern-growers. The forms of frond growing from one root of
Nephrolepis exaltata show remarkable variety.
In conclusion I may quote again from my friend Dr. Arber's
book Water Plants. She writes:—"Heterophylly is so wide-
spread that it appears to be a very general attribute of plant
life, rather than a rare and exceptional phenomenon" and in
those cases even where it might seem to be the result of adapta-
tion to special conditions, as in water plants, we may regard
it as not induced by its surroundings, but as occurring in those
plants "whose terrestrial ancestors were endowed with a strong
tendency towards heterophylly."1
1 Arber, A., l.c. 162.