The emergence of N. petersiana as sister to the remainder of
species in subg. Lotos is surprising but has also been confirmed
with a number of other chloroplast (Lo¨hne et al., unpublished
data) and nuclear ITS sequences (Borsch 2000). Leaf morphology
of N. petersiana sampled from Malawi is similar to subg.
Lotos, with margins being toothed and veins distinctly raised
from the blade beneath but without the pubescence characteristic
of that subgenus. However, the floral morphology of N. petersiana
strongly resembles subg. Brachyceras and contrasts with
subg. Lotos in its staminal appendages, short-triangular carpellary
appendages, and blue pigmentation (Mendonc¸a 1960). This
incongruous morphology was commented on nearly a century
ago by Gilg (1908), who mentioned that Conard (1905), who
had treated this species in synonymy under N. capensis Thunb.
of subg. Brachyceras, had annotated a sheet of this plant as a
mixture of these two groups. Verdcourt (1989) treated this taxon
under N. nouchali of subg. Brachyceras, using its leaf characters
to distinguish his var. petersiana (Klotzsch) Verdc. from the other
varieties of that species. The Malawan plants have large round
tubers that are used as food (Chawanje et al. 2001), but so far,
important information on the floral biology, degree of syncarpy,
and pollen morphology is lacking for N. petersiana that could
shed further light on its subgeneric affinities.