The first group of terrestrial plants are generally considered to be the bryophytes. These include mosses, liverworts, and hornworts.

Here's why:

* Early Evolution: Bryophytes are believed to have evolved from green algae around 470 million years ago, making them among the first land plants.

* Simple Structure: They lack vascular tissue, which means they don't have specialized tissues for transporting water and nutrients. This limits their size and restricts them to moist environments.

* Life Cycle: Bryophytes exhibit an alternation of generations, with a dominant gametophyte stage (the haploid, sexually reproducing stage). This is different from vascular plants, where the sporophyte (the diploid, spore-producing stage) is dominant.

While bryophytes weren't the first life to colonize land (early fungi and bacteria preceded them), they were the first group of plants to truly adapt to terrestrial life, paving the way for the evolution of more complex plant forms.