Charales

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iStoneworts
Scientific classification
Kingdom: Plantae Division: Charophyta Class: Charophyceae Order: Charales Family: Characeae
Genera
Chara Lamprothamnium Nitella Tolypella

The Charales are an order of green alga-like plants believed to be the closest relatives of the green land plants. They are branched, multicellular, chlorophyll-using plants that grow in fresh water. They are often called stoneworts, because the plants can become encrusted in lime (calcium carbonate) after some time. The "stem" is actually a central stalk consisting of giant, multinucleated cells. They are unique in having a whorl of small branchlets at each node in the stipe. Its antheridia and oogonia are protected by a layer of sterile cells when mature; the oogonium is oblong in shape and consists of a single egg, while the spherical antheridium is packed with threadlike cells that produce sperm. As a result, the Charales have the most complex structure of all green algae, if indeed they should be so labelled.