a species of _Miconia_. As in the hazel, the direction
of the adventitious leaf is inversely that of the primary one, the upper
surface of the supernumerary leaflet being turned towards the
corresponding surface of the normal leaf. A similar occurrence took
place in _Gesnera zebrina_, but the new growth in this case sprang from
the lower face of the leaf. Morren explains the appearances in question
by supposing that the supplementary leaf is one of a pair belonging to a
bud borne on a slender stalk. This stalk and one of the bud-leaves are
supposed to be inseparably united with the primary leaf. But there is
no reason at all for supposing the existence of adhesion in these cases;
no trace of any such union is to be seen. A much more natural
explanation is that, from some cause or another, development at the apex
of the petiole or on the surface of the nerves, instead of taking place
in one plane only, as usual, takes place in more than one, thus showing
the close relationship, if not the intrinsic identity, between the
leaf-stalk and its continuation, the midrib, with the branch and its
subdivisions. The form of the leaf-stalk and the arrangement of the
vascular bundles in a circle in the case of the hazel, before alluded
to, bear out this notion. Such cases are significant in reference to the
notion propounded by M. Casimir de Candolle, that the leaf is the
equivalent of a branch in which the upper portion of the vascular circle
is abortive.[395]

Compound leaves, as has been stated, occasionally produce an extra
number of leaflets; one of the most familiar illustrations of this is in
the case of the four-leaved shamrock (_Trifolium repens_), which was
gathered at night-time during the full moon by sorceresses, who mixed it
with vervain and other ingredients, while young girls in search of a
token of perfect happiness made quest of the plant by day. Linne, who in
this matter, at any rate, had less than his usual feeling for romance,
says of the four-leaved trefoil that it differs no more from the
ordinary trefoil than a man with six fingers differs from one provided
with the ordinary number. It should be stated that five and six
adventitious leaflets are found almost as frequently as four.

Walpers describes a case where the leaf of _T. repens_ bore seven
leaflets. Schlechtendal alludes to a similar increase in number in
_Cytisus Laburnum_, and many other instances might be cited.

For figures or descriptions of