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488
TYCHO NOR LINDH
Calenduleae, the fruit characters arc usuallv of great laxonomic value.
However, Ihese characters have to he used with a certaln degree of
caution, hecause in several cases the shape of the fruit is variable and
some types of fruit are hiconstant and appear sporadically in widely
separated species.
The dry fruit of the Compositae is usuallv designated an achene
in the literature and 1 have kept this term. As it is bicarpellary and
derived from an inferior one-seeded ovary, the möre exact term is
cypsela. The pericarp of this fruit thus consists not onlv of the ovarian
wall, as in the real achene (e.g. Ranunculus, Cliffortia), but also of the
adnate receplacle tube or calyx-tuhe of the floret.
In many species of the Calenduleae the nerves or ribs of the achene
are möre or less prominent. The primary ribs, when elevated, are blunt
or acute or extended into whigs, but the secondary ribs are nearly
always blunt.
In several species the achenes show only a slight suggestion of ribs
and in a large number of species 110 ribs at all are developed ön the
surface. Only hy cutting these achenes in Iransverse section is il
pos-sible lo detect nerves in their pericarp.
With regard to the morphology of the friiits, Calenduleae is
un-doubtedly the most abundantly differentiated tribe in the Compositae.
11 has two fundamentally different lypes of fruits, naniely disc achenes,
which are always bilateral (flattened), and ray achenes, which are never
bilateral, but usuallv trilateral (triangular) or terete. Besides, the ray
florets in one genus develop drupes.
Disc achenes are found solelv in the South African genera
Dimor-photheca and Castalis. They are stronglv flattened with the margins
expanded into wings. The number of Ihe nerves is reduced lo two, one
in each margin (cf. transverse section of disc achene in Lanza 1919,
tal). I, lig. 15). The disc achencs are always homomorphous and in their
circumference ohcordate—obovate -elliptic suborbiculate (I p. 47,
figs. 2 j, p; p. 59, fig. 3 f; p. 67, figs. 4 c, g, c, k: p. 83, figs. 5 d, j. k).
It is very probable that the ancestors of the species belonging to the
remaining genera of the tribe, once produced disc achenes of a similar
type. The disc achenes are light and, as they are provided with wings,
are well adapted for wind dispersal.
The ray flowers develop fruils in all llie genera in Ihe tribe excepl
Castalis. In contrast to the disc achenes, Ihese exhibit very great
variation in their shape. For instance, they are triangular or terete, straight
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