Which group of algae is believed to be the ancestor of land plants?

stonewort, and many green algae such as the Spirogyra.

Explanation:

As it was believed that the land algae were believed to be evolved from the stonewort plant and the blue-green algae like the cyanobacteria and the spirogyra that colonized the lands some 500 mn years ago was a freshwater alga. After which the first land plants occur about 470 million years ago, and they were in the form s of moss and liverworts of the vascular in origin.