Rene Zandbergen found similarities in the drawings of the Voynich Manuscript with the 14th century French manuscript Manfredus de Monte Imperiali (BNF Latin 6823, visit here ). So the following plant id proposal is based only on similarity with the picture of this manuscript - not on real plant.
fol. 65 of BNF Latin 6823 resembles a bit the plant on fol. 25r. According to the text it is supposed to be Bdellium (Commiphora wightii) - the cheaper version of Myrrh (Commiphora myrrha).
If there is myrrh, there must be frankincense :) On the next folio - 26r we find plant drawing with distant possibility for Boswellia sacra (frankincense).
UPDATE. Better choice for fol.26r may be Saw-leaved speedwell (Veronica austriaca)