In Large-flowered Bellwort (Uvularia grandiflora) the stem passes through or perforates the leaves.
In Sessile Bellwort (Uvularia sessilifolia) the stem is free from the leaves -- the leaves clasp the stem, but do not surround it.
Other species of flowers are also distinguished by this difference in leaf / stem structure. Why does such an trivial difference exist? What evolutionary force was at play? What advantage does one arrangement provide to each of the species?
