Calamansi seeds, like most other seeds, have three main parts:

1. Seed Coat: This is the outer protective layer of the seed. It's usually tough and waterproof to protect the inner parts from damage and drying out.

2. Endosperm: This is the food source for the developing embryo. It's rich in nutrients like starch, protein, and fats.

3. Embryo: This is the tiny plant inside the seed. It contains the root, shoot, and cotyledons (seed leaves) that will develop into a new calamansi tree.

These three parts are essential for the seed's development and the growth of a new calamansi tree.