>     Well until it is said not to be, they should be considered
> subsp.and not var. according to your key. Innocent until proven guilty!
It is rather the other way round. Don't change a name until you can 
prove that it is necessary (this is the philosophy of the Tokyo ICBN)!
 
> >>     The seeds are said to be subglobose in D.arenicola,
> >
> >Where do you have this from? The protologue says:
> >"seminibus elliptico-ovoideis reticulatis."
> >This is exactly the condition found in D.yutajensis.
> 
>     I'm basing myself on "The Botany of the Guayana Highland" by
> Maguire and Wurdack. There it says subglobose seeds for D.arenicola.
The protologue says something else. All available references/specimens 
should be considered.
>     Sorry,
No need to apologize.
> but as I understand it, papillae are projections from the
> seeds. Reticulated are the seeds of all D.montana, D.villosa,
> D.graminifolia, D.chrysolepis, D.communis, D.hirtella, D.colombiana, 
> and others except D.capillaris and D.intermedia among the Brazilian 
> species.
This is not entirely what I have seen. All vars. of _D.montana_, 
_D.hirtella_, _D.roraimae_, and especially _D.colombiana_ (cf. the 
drawing in the protologue!!) have papillate testa cells (sometimes 
with a central depression, making them appear reticulate to the 
unexperienced eye).
I do not consider the leaf shape differences you mentioned as 
significant here. If you consider the variability of the absolute 
dimensions within _D.roraimae_ (you yourself do not want to accept 
"D.montana var.robusta" as distinct) and especially between higland 
and savanna populations, size comparisons are IMHO immaterial here.
Kind regards
Jan