from
The Collaborative International Dictionary of English v.0.48
Quincuncial \Quin*cun"cial\, [L. quincuncialis, from quincunx.
See {Quincunx}.]
[1913 Webster]
1. Having the form of a quincunx.
[1913 Webster]
2. (Bot.) Having the leaves of a pentamerous calyx or corolla
so imbricated that two are exterior, two are interior, and
the other has one edge exterior and one interior; as,
quincuncial [ae]stivation.
[1913 Webster]
{Quincuncial phyllotaxy} (Bot.), an arrangement of five
leaves in a spiral, each leaf two fifths of a circle from
the next.
[1913 Webster]