Plants are complex multicellular eukaryotes with specialized reproductive organs, which (with very few exceptions) obtain their energy through photosynthesis, synthesize their food from carbon dioxide, have sterile tissue within the reproductive organs, and are primarily terrestrial.
On a microscopic level, plant cells are eukaryotic, with a cell wall composed of cellulose and plastids surrounded by two membranes. These usually take the form of chloroplasts, which conduct photosynthesis and store food in the form of starch, and characteristically are pigmented with chlorophylls a and b, generally giving them a bright green color. Plant cells also generally have an enlarged central vacuole or tonoplast, which maintains cell turgor and keeps the plant rigid. They lack flagella and centrioles except in certain gametes.
The simplest plants are the star plants, the lithopytes, the flatmosses, the fern-trees, and the tooth rushes. More "advanced" plants include the acrid trees, the starch plants, the cone reeds, the scale berry plants, the spiny prickles, and the scale bark trees.