Christoph Oberprieler The Systematics of Anthemis L. - Herbmedit.org

22 Oberprieler: Anthemis in N Africa
conspicuous inhibition zone is found beneath the capitulescence of the main axis, and side
axes will arise from the basaI nodes of the main axis after its capitulescence has flowered
(Fig. ID). For convenience, such side axes are termed stems in the present revisiono
Some annual N African representatives of Anthemis (e.g. A. tenuisecta, A. confusa, or
A. glareosa) are characterised by a prostrate habit. Their main axis is reduced and its basaI
intemodes are extremely short (Fig. lE). Reduction of the main axis is often so complete
that branching occurs directly from the taproot (Fig. lF). The larger and usually petiolate
lower cauline leaves that normally make up the basaI rosette are almost totally missing;
most leaves are sessile and resemble upper cauline leaves of plants with a normally developed
main axis. This character may be used to distinguish between N Tunisian A. ubensis
and the closely related C Tunisian A. confusa: While A. ubensis has an erect habit with a
main axis and leaves that successively decrease in size and dissection from base to top,
A. confusa is characterised by prostrate habit and poorly dissected leaves.
In perennial N African representatives of the genus, the trend towards reduction of the
main axis is well marked, but realised in a different way. The current year's shoots arise
from the lignified bases of primary and subsequent shoots of the last years (Fig. lG).
Sometimes the main axis is basally more or less completely fused with the taproot to form
a ± subterranean rootstock (caudex) that often bears both non-flowering and flowering
shoots (Fig. lH). The capitulescences are often reduced to a single capitulum, and rarely
more than three (up to lO) capitula.
The stems are usually herbaceous in their distaI part but conspicuously lignified basalIy,
particularly in perennials. Stems formed by the main axis are usualIy straight basally,
while those corresponding to side branches or bome on a rootstock are basalIy bent upwards.
In species with a procumbent habit, only the capitulescence or single peduncles are
lifted above the ground. In alI cases, the stems are round in cross-section and somewhat
sulcate. They are usually green, often tinged with redin the lower half.
In Anthemis maritima in particular, and to a lesser extent in the other perennial representatives
of A. sect. Hiorthia, the lower stem nodes may be beset with accessory roots.
Stem length varies considerably with growth conditions: in the perennials of Anthemis
sect. Hiorthia it is 20-40 cm, in representatives of A. sect. Anthemis and sect. Maruta
usualIy up to 25 cm, but under favourable conditions sometimes much more (e.g. in
A. gharbensis 60 cm, A. cotula 90 cm). Accordingly, the diameter of stem bases may vary
between less than 1 mm in poorly developed plants up to 3 or occasionalIy 6 mm in vigorously
growing annuals and some perennials.
Indumentum
The indumentum in most N African representatives of Anthemis consists of biseriate
glands and medifixed covering hairs, as already found by Napp-Zinn & Eble (1980).
Medifixed hairs are usually bome on a stalk formed by 2-4 (sometimes even up to 7)
more or less isodiametic celIs and a large, strongly elongated apical celI that is symmetrically
or asymmetricalIy suspended at the tip of the stalk. While the stalks may reach a
length of c. 50-80 !lm, the length of the apical celI is usualIy found to be 400-1000 !lm. In
some species, extremely asymmetrically medifixed apical cells are found. Sometimes,
especialIy on peduncles and involucral bracts, asymmetry is so marked that the apical celI
is no longer medifixed and an uniseriate flagellar covering hair is formed. These hairs are