stomary forms of
organs.

[373] 'De Antholys,' p. 32, Sec. 38.

[374] 'Bull. Acad. Belg.,' xvii, part 2, p. 131, c. tab.

[375] See Cramer, 'Bildungsabweich,' pp. 17, 55, 82, 65. See also Lucas,
'Verhandl. des Bot. Vereins. Brandenb.,' heft 1, 2, _Anchusa_. Christ,
'Flora,' 1867. pp. 376, tab. 5, 6, _Stachys_.

BOOK III.

DEVIATIONS FROM THE ORDINARY NUMBER OF ORGANS.

To a certain extent the number of the organs of a plant is of even
greater consequence for purposes of classification than either their
form or their arrangement; for instance, the number of cotyledons in the
embryo is made the chief basis of separation between the two great
groups of flowering plants, the monocotyledons and the dicotyledons. In
the one group, moreover, the parts of the flower are arranged in groups
or whorls of five; in the other the arrangement is ternary. In mosses
the teeth of the peristome are arranged in fours, or in some multiple of
that number. So far as the larger groups are concerned, and also in
cases where the actual number of parts is small, the numerical relations
above described are very constant; on the other hand, in the minor
subdivisions, and especially where the absolute number of parts is
large, considerable variation may occur, so that descriptive botanists
frequently make use of the term indefinite, and apply it to cases where
the number of parts is large and variable, or, at any rate, not easy to
be estimated.

Considered teratologically, the changes, as regards the number of
organs, are readily grouped into those consequent on a decreased and
into those resulting from an increased development. The alteration may
be absolute or relative. There may be an actual deficiency in the number
of parts or an increase in their number, but in either case the change
may be simply a restoration of the primitive number, a species of
peloria, in fact. An increased number of parts, moreover, may depend not
so much on the formation of additional parts as on the subdivision of
one.

It seems also desirable to treat separately those cases in which there
is an increased number of buds either leaf-buds or flower-buds, as the
case may be, as happens in what is termed prolification. This formation
of buds occurring, as it does, often in unwonted situations is treated
of under the head of alterations of arrangement, the mere increase in
number being considered of subordinate importance as contrasted with the
altered dis