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STUDIES IN THE CALENDULEAE
495
Fig. 8. Approximate distribution of Glbbiiria Gass. As regards I lie shape of the
achenes this genus represents a line of evolution almost convergent with that
exhibited by Calendula in the northern hemisphere.
c, k) and of annulate or imperfectly annulate achenes in Calendula
(I i). 361, fig. 38 h and Lanza, 1919, tab. II, figs. 39—41; tal). IX,
figs. 1 1), c and 2 c; tab. X, fig. 1 h). The disparity between Ihese types
of achenes is considerable, and with my present knowledge of Ihe
shapes of Ihe achenes in Osteospermum and Calendula I have nol felt
il necessary to unite t hese genera to form a single one.
Calendula represents a special line of evolution in the |ribe as
regards the morphology of the achenes, all the species having annulate
achenes of mticli advanced type. Further, the genus has a centre of
development of its own in Ihe Mediterranean region, which is very far
remote from the other centre of the tribe in South Africa. Only a very
few of the northern oulliers of Osteospermum establish contact with
the southerninost outposts of Calendula.
In the southern hemisphere Calendula tias a coimterpart in the
small genus (iibbaria, which, in Ihe matter of Ihe shape of the achenes,
represents a line of evolution almost convergent with |bat exhibited by
Calendula. The Gibbaria species have, in fact, strongly incurved and
reniform achenes (I p. 361, figs. 38 a—f). These achenes mainly differ
from those of the Calendula species by containing a closed ventral
cavity (op. elf., fig. 38 c, f). (iibbaria s achenes most resemble in shape
the Calendula achenes, which are cymbiform or intermediate between
annulate and cymbiform (Lanza tal). 11. figs. 37, 38; tab. IV, fig. 4 b:
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