Acorns, maple seeds and the seeds of legumes (a family of plants that includes beans, peas and lentils) are examples of dicot seeds. The common characteristic of these seeds is that they contain two seed leaves inside the seed coat.
In 1682, John Ray introduced the taxonomic division of flowering plants into monocots and dicots, a division that is still widely used as of 2015, even though there are some plants that mix characteristics of the two groups. As a general rule, monocot seeds differ from dicot seeds in having only one seed leaf rather than two within the seed coat. In addition, the seed leaf of a monocot seed does not contain the endosperm that feeds the new plant, while the seed leaves of dicot seeds do contain endosperm.