The article by Dr. Cheek on Mr. Lowrie's book (CPAU2) was published
(together with a (poor) photograph of the type specimen of D.omissa)
in CPN 19(3/4):82-84 (1990).
D.ericksoniae (which was originally identified with _D.omissa_
by Rica Erickson!) matches both the description and the type specimen
of _D.omissa_ much better (broad sepals, subglobose fruiting calyx,
large petals, large leaves) than the plant described and depicted in
the above cited book as "D.nitidula subsp.omissa" (misapplied name),
which AFAIK has no valid name until this date.
Kind regards
Jan