Phylum Chlorophyta
Chlorophyta is a division of green algae, informally called chlorophytes. It is generally accepted that early chlorophytes gave rise to the plants. Chlorophytes store their food in the form of starch in plastids and, in many, the cell walls consist of cellulose. Unlike in plants, there is no differentiation into specialized tissues among members of this division, even though the body, or thallus, may consist of several different kinds of cells. This is the most diverse group of algae, with over 7,000 species. One of the ways to identify Chlorophyta is by their small subunit rDNA.
Green algae
The green algae include unicellular and colonial flagellates, most with two flagella per cell, as well as various colonial, coccoid and filamentous forms, and macroscopic, multicellular seaweeds. They're an ancient group according to the fossil record, green algae are extremely diverse, and are often the dominant algae in freshwater environment. They can provide food for newly born fish and they also oxygenate the water. Green algae are extraordinarily diverse morphologically and are separated taxonomically into two phyla, Chlorophyta and Charophyta. Sea lettuce is a bright green algae composed of lobed, ruffle-edged leaves that are coarse and sheet-like and resemble a leaf of lettuce. The leaves may appear flat, thin, broad, and often rounded or oval. Its leaves are often perforated with holes of various sizes. Almost no stalk exists at the point of attachment, and no true roots are present.