y variously developed in different cases; sometimes it is a mere
"collar" bearing the cotyledons, while at other times it is of
considerable size. Generally it does not give origin to shoots or leaves
other than the seed-leaves, but occasionally shoots may be seen
projecting from it below the level of the cotyledons. This happens
frequently in seedling plants of _Anagallis arvensis_, _Euphorbia_
_peplus_, and other species, _Linaria vulgaris_, some _Umbelliferae_,
&c.[151]

=Adventitious formation of leaves.=--The term phyllomania has been
vaguely applied both to the production of an unwonted number of leaves
and to their development in unusual situations. Under the present
heading the latter class of cases are alone included. The extraordinary
tendency in some Begonias to develop leaves or leafy excrescences from
their surfaces is elsewhere alluded to, and is, in reality, a species of
hypertrophy or over-luxuriant growth.

In some flowers where the inferior ovary is supposed to be, in part at
least, formed by a dilatation of the top of the flower-stalk, leaves
have been met with proceeding from the surface of the ovary or fruit, as
in _Crataegus tanacetifolia_, roses, pears, gooseberries, &c. In a
specimen of _Nymphaea alba_ I have met with scale-like leaves projecting
from the surface of the fruit (or torus?), and which did not appear to
be metamorphosed stamens or styles (fig. 76).

[Illustration: FIG. 75.--Leaf proceeding from hip of the Rose.]

[Illustration: FIG. 76.--Leaves proceeding from the ovary of
_Nymphaea_.]

For other illustrations of increased leaf-formation, see Multiplication
of foliar organs.

[Illustration: FIG. 77.--_Leontodon_. Scape with two leaves; the bracts
of the involucre are also leafy.]

=Production of leaves on a usually leafless inflorescence.=--The
development of the bracts of an inflorescence to such an extent that
they resemble ordinary leaves is elsewhere alluded to as of common
occurrence. It happens far less frequently that leaves are developed on
an inflorescence usually destitute of them, without any metamorphosis or
substitution, and without any formation of adventitious buds, such as
happens in prolification. Such a partial change from a floriferous to a
foliiferous branch may be seen in a specimen of _Sambucus nigra_ in the
Smithian herbarium in the Linnean Society, where the ultimate branches
of the cyme bear small leaves. My attention was directed to this
specimen by