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STUDIES IN THE CALENDULEAE
487
Fig. (i. Approximate distribution of sect. Blaxium in the genus Osteospermum. The
distribution of O. caulescens Harv. in this section is of great phytogeographical
interest, because it oeeurs hoth in the Drakensberg area and in Angola, a gap of
almost 2000 km separating its locality in Angola from the Drakensberg centre. It
indicates a much wider distribution of this section during an earlier period. In this
very natural section there is a form series ol disc styles almost connecting the style
type of Dimorphotheca with that of Osteospermum. However, half the number of
species have disc styles of a pronounced Osteospermum type. It is not impossible
that some of the other species comprise hoth biotypés with only 9~ster’’e disc
florets and such with a lew £-fertile disc florets. Hitherto I have only seen ray
achenes of these species, which is the reason why I have placed the section
in Osteospermum.
perhaps rather to be classifiecl as a subspecies of il Thus. in certain
cases the colour cail only be used as a specific charader with some
hesitation.
The derivation of differenl fruit tvpes in the Calenduleae does not
usuallv cause any great difficulties, because intermediate forms connecl
nearly all the extreme types. In the following, 1 shall give a survey of
|bose principal types and form series of fruils which are of importance
in the discussion of interrelation and evolution in the tribe.
In spite of the occurrence of several heterocarpous species in the
32 Botaniska Notiser 19tC>.
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