ment of a
single leaf by two leaves. The arrangement in Prof. Dickson's leaf may
be thus represented: [Symbol: )OO( with X above]. The nature of the case
may be even better seen by comparison with the normal arrangement, which
would be [Symbol: (OX turned 90 degrees ccw], while in those cases where
the fission of the leaf occurs in the same plane as that of the primary
lamina, as where a leaf splits into two lobes at the apex, with a midrib
to each, the arrangement is as follows: [Symbol: OX turned 90 degrees
ccw, with 2 arcs below forming a half circle], the X in all cases
representing the position of the axis, the O that of the axillary bud,
and the [Symbol: ( turned 90 degrees ccw] that of the laminae."

[519] Linn., 'Phil. Bot.,' Sec. 274. The term "_crispa_" is surely
preferable to that of Re, "phyllorhyseme."

[520] See C. Morren, "Consid. sur les deformations," &c., in 'Bull.
Acad. Belg.,' 1852, tom, xix, part 3, p. 444; and as to ferns, see
Moore, 'Nature-Printed British Ferns,' 8vo ed., where numerous
illustrations are given.

[521] 'Bull. Acad. Belg.,' t. xix, p. 224, tab. i; and 'Gardeners'
Chronicle,' 1865, p. 865.

PART II.

ATROPHY.

Under the head of atrophy are included those cases wherein the organs
affected are actually present, but in a dwarfed and stunted condition as
compared with surrounding parts.

The diminished size is, in such instances, obviously due to a partial
development and to an arrest of growth at a certain stage, from the
operation of various causes, either external or inherent to the
organization itself. It may affect any part of the plant, and exists, in
very varying degree, in different instances, being sometimes so slight
in amount as not to preclude the exercise of the functions of the part;
while in others, the structure is so incomplete that the office cannot
be performed. These differences depend, of course, upon the stage of
development which the organ had reached when its growth was checked. For
practical purposes atrophy may be distinguished from suppression by the
fact that in the latter case a certain element of the flower or plant
which, under ordinary circumstances, is present, is entirely wanting,
while, in the former class, it exists but in a rudimentary condition.

Again, atrophy is to be separated from that general diminution in the
size of the whole plant or of distinct parts of that plant which is
comprised under the term "nanism." Thus the severa