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48(5
TYCHO NOR LINDH
to Osteospermum at a låter period than the other species of the genus.
In the phylogenetic chart (fig. 9. p. 497) I have indicated this recent
development hy an arrow drawn from the circle of the recent
Dimor-photheca to that of Osteospermum.
The morphology of the slyles in Castalis nudicaulis and the
above-mentioned species in sect. Blaxium of Osteospermum indicates the
course of evolution. Castalis and Osteospermum have developed from
Ihe genus Dimorpliotheca through gradual reductions of the pistils, and
nearly all stages of this reduction can he observed in the stvles of these
species. The occasional appearance of möre or less distinct stigmatic
papillae ön the ray and disc slyles respectively in these species shows
that they have not yet entirely reached the final stage of their evolution
in regard to the reduction of Ihe pistils.
lf future research should show that species of Castalis and sect.
Blaxium in Osteospermum normally comprise biotypes that also have
?-l’ertile ray and disc flowers respectively it will be difficult to
main-tain Dimorpholheca,1 Castalis and Osteospermum as independent
genera.
In attempting to delimit Dimorpliotheca from Osteospermum and
Castalis I have not been able to find any möre characters than the
dissimilar development of the organs of fructification and the
conse-quent differences in the fertility and sterilitv conditions. This
Classification is meant to reflect the phylogenetic evolution in the tribe.
Since 1865, wlien Harvey published bis revision of tribus
Calenduleae in Flora Capensis III, the delimitation of Dimorpliotheca and
Osteospermum has been based upon the arrangement of the involucral
scales, bill 1 have found this charader to be useless for keeping these
genera apart (I p. 21). Nor could I lise the colour of the ray flowers
as a generic charader in this case, because several species of
Dimorpliotheca, viz. D. sinuata, D. chrijsanthemifolia, I), montana and I),
polyp-tera, have yellow flowers just as the Osteospermum species. The
vellow-flowered 1). sinuata is so closely allied to 1). phwialis that it ought
1 Afler having prepared this papcr. I received a collection of Dimorpliotheca
from Cape Town. The material of D. montana also proved to contain two specimens
with well developed disc achenes, bul enlirelv without ray achencs. In this case
I have no reason lo suspect any abnormalily in the flower-heads. The material
indicates that D. montana is a transitional species between Dimorpliotheca and
Castalis. The species population would in (bat case comprise one group of biotypes
with fertile ray florets and one group ol biotypes with sterile ray florets. lf several
similar cases become known, then Castalis cannot be treated as such a higli
taxo-nomical unit as a genus.
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