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

20 Oberprieler: Anthemis in N Africa
9. MorphologicaI features
Duration and life form
The majority of N African representatives of Anthemis are annuals belonging to A. sect.
Anthemis, sect. Maruta, and sect. Cota. The annual habit may be interpreted as an adaptation
to the dry semi-desert and steppe habitats of the adjacent areas of the Sahara, and to
disturbed habitats or arable fields. A. stipa rum, A. confusa, or A. glareosa are prostrate
annuals with reduced main axes and procumbent stems with smallleaves, found in natural
stony and sandy habitats of the deserts. The vigorous growth of A. gharbensis and
A. cotula, found as weeds in arable fields and along field margins in more hurnid areas,
forms the opposite extreme habit of therophytic Anthemis in N Africa.
Anthemis sect. Hiorthia contains short- to long-lived perenni al herbs which are restricted
in N Africa to the hurnid areas of the coasts (A. maritima) or to the mountains of
the Atlas ranges of Morocco, Algeria, and Tunisia (A. abylaea, A. pedunculata,
A. punctata, A. eretica subsp. columnae). At least A. pedunculata is capable to flower and
set fruit already in the first year, and especially diploid plants are often found growing as
weeds in arable fields, so that the differences between annual and perenniallife form seem
not to be too c1ear-cut in this species. However, in better growing conditions
A. pedunculata is c1early a short-lived perennial, with annual shoots arising from a woody
stock (pleiocorm) formed by the bases of the primary and subsequent annual shoots.
Tetraploid plants of A. pedunculata, along with representatives of A. abylaea, A. punctata,
and A. eretica subsp. columnae, also grow as pleiocormous hemicryptophytes. Observations
in the field and herbarium suggest that most representatives of these species have
life spans of three to five years.
Roots and rhizomes
The root system type is c10sely correlated with habit and duration. In ali annuals of
Anthemis sect. Anthemis, sect. Maruta, and sect. Cota, taproots are found. The perennials
in A. sect. Hiorthia are characterized by a woody caudex formed by the lignified bases of
previous years' shoots fused with the basai taproot. In younger individuals the caudex may
be unbranched and only partly subterranean, in older ones branched and completely subterranean
caudices (pleiocorms) may be found. In the perennial species, especially in
A. maritima, accessory roots bome at the basai stem nodes are frequently observed which
are missing in annuals, even if procumbent.
Growth habit, stems and capitulescence
The most simple condition in the organisation of stem and disposition of capitula found
in Anthemis is shown in Fig. lA: the mai n axis is erect and ends in a cymose capitulescence
characterised by a terminai capitulum which flowers first. This type of capitulescence
organisation is found in most N African annuals, e.g. A. austriaca, A. ubensis, or
A. monilicostata. Unsuitable growing conditions like drought or malnutrition may considerably
reduce the number of developing branches and lead to poor capitulescences of few
or a single capitulum.
A more complicated condition of stem and capitulescence organisation results when side
axes are added beneath the main capitulescence (Fig. lB). Troll (1964) and Panero (1992)
use the term parac1adia to designate these accessory flowering branches, each of which