he upper part; each of these lobes seemed to be as large as
the limb of an ordinary leaf. Above these was another very broad one,
apparently entire, but evidently produced by a complete cohesion of two.
This completely fused leaf alternated in position with the imperfectly
fused one below it; the alternation is explained by supposing that the
opposite leaves of each pair were directed one towards the other, and
became fused, and that thus resulted the displacement. The dislocation
of the organs took place in one direction for one pair of leaves, and in
another direction for the other pair, hence the alternation. Thus,
leaves normally opposite and decussate may, by fusion, become alternate.
A similar instance occurred to the writer in _Lysimachia vulgaris_,
wherein the changes arising from fusion and suppression of parts, &c.,
were very considerable; as far as the leaves were concerned they
presented the following arrangement in succession from below
upwards:--first verticillate, then opposite, then spirally alternate,
lastly opposite.[94] The term "diremption" has sometimes been applied to
cases where leaves are thus apparently dragged out of position.

In _Tradescantia virginica_ I have met with opposite connate leaves;
the altered position, however, being due to the union of two stems.

[Illustration: FIG. 40.--Large-coloured leaf occupying the position of
the inflorescence in _Gesnera_, after Morren.]

[Illustration: FIG. 41.--Ordinary arrangement of leaves in fascicles of
three in _Pinus pinea_ and unusual arrangement of leaves of same plant
in spires.]

Twisting of the stem is a frequent cause of the displacement of leaves
(see spiral torsion), as also hypertrophy, whether that excess of
development take place laterally or lengthwise (see elongation). Atrophy
or suppression will also frequently bring about an alteration in the
position of leaves; sometimes in such a manner that the place of the
suppressed organ is occupied by another one. One of the most curious
instances of displacement of leaves arising from suppression is that
mentioned by Morren,[95] where, in _Gesnera Geroltiana_, a large leaf
apparently occupied the extremity of the axis, a position which, under
ordinary circumstances, no leaf could assume. The explanation given by
the Belgian professor is, that the axis in this case, instead of
throwing off a pair of leaves, one on each side, had from some cause or
another produced only one; this one not