Garden with Insight v1.0 Help: seedling leaf (cotyledon)

Seedling leaves or cotyledons are the first leaves to appear on a plant. When a seed develops in the ovary of a plant, seedling leaves form there with all the machinery needed to carry out photosynthesis. The seedling leaves lie in the seed while it is dormant like inflatable emergency rafts. When the seed germinates it takes up water (imbibes water) and the seedling leaves expand. The seed's tiny stem grows using reserves in the seed and the leaves are brought above the soil and begin the process of photosynthesis to capture energy and grow new plant parts.

Plants whose seeds have two seedling leaves are called dicotyledons and include most flowering plants (flowers, vegetables, shrubs, trees). Plants whose seeds have one seedling leaf are called monocotyledons and include the grasses and cereal grains (wheat, rice, oats, barley, etc), bamboo, palm, lilies and others. These are some other fairly consistent differences between monocots and dicots:

Monocots have parallel leaf veins; dicots have branching leaf veins.
Monocots usually have flower parts in sets of three; dicots usually have flower parts in sets of four or five.
Monocot stems never become woody and grow in thickness (secondary growth); some dicots do.
Monocots rarely branch; dicots do much more often.