[Illustration: FIG. 28.--Bifurcated frond, _Scolopendrium vulgare_.]

A. Braun describes a singular case in a leaf of _Irina glabra_
wherein the blade of the leaf on one side was deeply and irregularly
laciniated, the other side remaining entire. (Verhandl., d. 35,
Naturforscherversammlung, tab. 3.) Laciniate varieties of plants are of
frequent occurrence in gardens where they are often cultivated for their
beauty or singularity; thus, there are laciniated alders, fern-leaved
beeches and limes, oak-leaved laburnums, &c. A list of several of these
is subjoined. A similar fission takes place constantly in the cotyledons
of some plants, sometimes, as in _Coniferae_, to such an extent as to
give an appearance as if there were several cotyledons.[73]

It is not always easy to recognise, at a first glance, whether the
division be the result of disunion or of an incomplete union of two
leaves, but we may be guided by the number of leaves in the cycle or the
whorl. The number is complete in cases of partial disjunction, while in
cases of fusion it is incomplete. Again, in instances of disjunction,
there is only one point of origin, but, when two leaves are grafted
together, two such points may generally be detected at the base of the
leaf, or a transverse section of the leaf-stalk will show indications of
fusion. The number and position of the midribs will also serve as a
guide, as in cases of fusion there are generally two or more midribs,
according to the number of fused leaves; but as Moquin well remarks,
this latter character cannot be always depended upon, for the median
nerve may divide without any corresponding separation of the cellular
portions of the leaf. The author just quoted cites examples of this kind
in _Cardamine pratensis_, _Hedera Helix_, _Plantago major_, _Geranium
nodosum_.

The following list of plants commonly producing leaves that are cleft or
divided, to a greater extent than is usual in the species, is mainly
taken from one given by Schlechtendal, 'Bot. Zeit.,' 1844, p. 441, with
additions from other sources. The ! indicates that the author has
himself met with the deviation in question. Many are cultivated as
garden varieties under the names here given.

Trollius europaeus dissectus.
Chelidonium majus laciniatum!
Glaucium luteum.
Brassica oleracea!
Tilia parvifolia laciniata.
asplenifolia!
Acer platanoides laciniatum.
crispum.
AEsculus Hippocastanum incisum!
a