Lathyrus sylvestris – Flat pea

Flat pea is an herbaceous perennial commonly found in different habitats such as hedges, wood-borders, scrub and on rough banks. It belongs to the Fabaceae family.
Floral formula: 5S/ 5 P/ 10 St/1 C; zygomorphic corolla (papilionaceous); stamens either monadelphous (10 fused) or diadelphous (9 fused + 1 free).

The uppermost petal is known as the « standard », the lateral two as the « wings » and the lowest two are joined to form the « keel »
Paraffin cross sections (8 µm thick) have been made at two levels in a floral bud and stained with toluidine blue: ovaries and stamens (see photographs below).

Level of ovaries
Level of stamens