Monocots are a class of angiosperm, or flowering plant, distinguished from dicots. The distinction was first established by botanist John Ray in 1682. Scientists today do not consider Ray’s description perfect, however monocots are still the most popularly known classification of angiosperms. The terms monocot and dicot are short for the longer names Monocotyledonae and Dicotyledonae, which refer to the number of cotyledons, or "seed leaves," in the plant's embryo; one and two, respectively.
Monocots are distinguished from dicots by their physical characteristics. In addition to having a single cotyledon in their embryo, they also feature pollen with a single furrow or pore, while dicot pollen has three furrows. Most of the other monocot features are easier for the casual observer to identify.
Perhaps the simplest way to distinguish monocots from dicots is by counting flower parts. Petals, stamens, and so on tend to appear in multiples of three on monocots, while dicot flowers tend to have parts divisible by four or five. While this is sometimes the easiest way to figure out what type of angiosperm you are dealing with, it is not always reliable and may be difficult to determine in plants with elaborate flowers containing many parts.
In monocots, the leaf veins tend to run parallel to the length of the leaf, while dicot leaves feature more branching, reticulate veins. Similarly, the vascular system in the plant's stem, which serves to transport water and nutrients through the plant, appears in a regular, cylindrical pattern in the dicot stem, but a more random, scattered pattern in the monocot stem. Therefore, a dicot may be identified by looking at a cross section of the stem and marking a ring of small circles. Both of these methods for distinguishing monocots from dicots are not foolproof.
The roots of monocots and dicots also grow in different ways. Dicots feature an apical meristem, an area of undifferentiated embryonic tissue at the bottom of the stem that produces roots throughout the plant's lifetime. Monocots, on the other hand, have adventitous roots that arise from nodes on the stem.
Monocots are also distinguished by the lack of secondary growth, or wood. Some dicots cannot produce wood, however no monocots can. Some monocots appear to be woody, such as palm trees, but the wood-like trunk is actually an accumulation of leaf bases.