To solve this problem, we need to identify the plant that exhibits vexillary aestivation and diadelphous stamens. Let's analyze each option:$\newline \bullet$Option 1: Colchicum autumnale$\newline$ - Colchicum autumnale, commonly known as autumn crocus, does not exhibit vexillary aestivation or diadelphous stamens.$\newline \bullet$Option 2: Pisum sativum$\newline$ - Pisum sativum, commonly known as pea, belongs to the family Fabaceae.$\newline$ - It exhibits vexillary aestivation, where the largest petal (standard) overlaps the two lateral petals (wings), which in turn overlap the two smallest petals (keel).$\newline$ - The stamens in Pisum sativum are diadelphous, meaning they are arranged in two groups: one group of nine stamens fused together and one free stamen.$\newline$ - Therefore, Pisum sativum shows both vexillary aestivation and diadelphous stamens.$\newline \bullet$Option 3: Allium cepa$\newline$ - Allium cepa, commonly known as onion, does not exhibit vexillary aestivation or diadelphous stamens.$\newline \bullet$Option 4: Solanum nigrum$\newline$ - Solanum nigrum, commonly known as black nightshade, does not exhibit vexillary aestivation or diadelphous stamens.$\newline$Based on the analysis, the correct option is Option 2: Pisum sativum, as it shows vexillary aestivation and diadelphous stamens.