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484
TYCHO NOR LINDH
I i O) is t hus mark two different lines of development from the ray and
disc pistil types of Dimorphotheca, for I regard it as evident that all
the species in the tribe Calenduleae had both ?-fertile ray and disc
florets in an earlier stage of their evolution and that their pistils at that
time were developed in the main as |hey now are in Dimorphotheca.
Bisexuality is 110 doubl a primitive charader in Compositae. The former
line of evolution is far from vigorous, being represented solely bv the
genus Castalis. The latter line of development, ön the other liand,
coni-pletely predominates in the tribe.
In the sterile pistils the development of both ovary and style is
incomplete. By studying the shape and structure of the style, above all
the presence or absence of stigmatic papillae, it is easy to decide whelher
a floret is fertile or sterile, except in a few cases which I am now going
to discuss.
Judging from Ihe style types, some of the species in the tribe
Calenduleae have differentiated from the genus Dimorphotheca
com-perativelv recently. In Castalis nudicaulis and some species in sect.
Blaxium of the genus Osteospermum, viz. O. fruticosum, O. Barberiae,
O. jucundum and O. caulescens,1 the reduction of the ray and of the
disc styles respectively lias, in fact, not advanced as niuch as in o|ber
species in tliese genera (1 p. 25). In occasional individuals of these
species the normallv non-stigmatic styles may show suggestions of
stigmatic papillae. It is therefore not quite impossible that in rare cases
achenes develop in these normallv 9-sterile florets.
Calenduleae sensu stricto, i.e. with the exchision of the
morpho-logically much deviating genera Dipterocome, Ëriacliaenium and
Garu-leum, forms a very natural tribe as regards the floral structure. The
differences in the shape and development of the styles are partially
bridged över by a few almost intermediate forms mentioned above, and
no difficulties are encountered in tracing Ihe styles of the various species
from tliose occurring in Dimorphotheca.
In the type of the genus Castalis, C. Tragus, the pistils of the ray
florets have been reduced most and styles are often entirely lacking.
Ön the other hand, corresponding pistils in C. nudicaulis are only
slighUy reduced and are normallv furnished with a style (I p. 83, fig.
5e—g). This is usually bifid and without stigmatic swellings, a
suggestion of stigmatic papillae being found upon it in exceptional cases,
1 The distinguishing charaeters of the three tast-mentioned species are in fact
very slight, and (hey ought perhaps rather to be treated as tower taxonomical unils
of one species, the oldest name of which is O. Barberiae.
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