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STUDIES IN THE CALENDULEAE
473
1. The Chief Centres of the Tribe Calenduleae.
The Calenduleae occur in Africa, Soulhern and Central Europe,
Western Asia and, taken in ils widest circumscription (Bentiiam et
Hooker 1873—187(>; Hoffmann 1894). this Irihe also comprises a
monotypic genus oecurring in Soulh America. From a
phytogeogra-phical poinl of view Ihe following cenlres are of the greatesl significance.
1. The Mediterranean cent r e. The genus Calendula
has ils main distribution in the Mediterranean region and, ön the eastern
outskirts of this zone, Dipterocome also occurs. Only one species of
Osteospermum penetrates into the Mediterranean, viz. O. Vaillantii
occurring in the south-eastern part.
2. T h e S o u t h A f r i c a n cent r e. The Calenduleae has its
maximum concentration of species in the Cape realm, but the
southern-most part of the Paleotropical realm has a larger number of species
belonging lo this tribe than the Cape realm. In Soulh Africa the tribe
is represented bv the genera Dimorphotheca, Castalis, Osteospermum,
Gibbaria, Chrysanthemoides (and Garuleum).
In the Mediterranean region Calendula exhibits its greatest
diffe-rentiation into taxonomical units. The gene centre of the genus seems
lo be situated in the western part of this region. From the areas
sur-rounding the Mediterranean representatives of the genus radiale in every
possible direction (map fig. 1) but with only a lew species. In the west,
species of Calendula occur in the Atlantic Islands, viz. the Canary
Islands, the Madeiras and the Azores. The occurrence of one endemic
species in Madeira is of great phytogeographical interest. In Ihe north
one species of the genus extends iniö Ihe Central European region as
far as Ihe middle of France and the soulh of Germany. In the east
the genus penetrates far into Ihe Ponlic-Central Asiatic steppe region
to the south-east coast of the Caspian Sea and Ihe south-east of Persia.
In the soulh Calendula reaches down into Ihe North African-Indian
desert zone with outliers in Ihe Ahaggar (Hoggar) Mountains in the
Central Sahara and in Ihe Yemen Mountains in tropical Arabia.
Dipterocome is foiind only in the easternmost portion of the
Mediterranean region, namely in Palesline, whence it spreads far into Persia
and Afghanistan.
In South Africa the tribe has allained ils maximum differentiation in
genera and species. As regards Ihe wealth of biotypes only a very few
of the South African species are comparable with those in the
Mediterranean region, however. Many of the South African species of the
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