The third petal is the lip. Orchids share this structure with lilies and irises.

VOA: special.2010.04.06

So, that's his gift to us: the Lewis structure, and the idea that you could share electrons and form a covalent bond.

这就Lewis给我们的礼物，Lewis结构，你能够通过公用电子,形成共价键。

麻省理工公开课 - 固态化学导论课程节选