They use the same strengthening and conducting tissues that were found in the Liverworts but they produce them in sufficient quantities to achieve verticality. These are still small plants which rarely top 10 cm. The most complex species had photosynthetic and subterranean stems . The latter are root-like and produce Rhizoids. These are still Small Plants reaching only a few cm.
Many species are terrestrial but a significant number are epiphytes.
They typically grow in wet areas but some can grow in extremely cold and dry environments where they are Pioneers. Moss Leaf with a prominent Nerve Polytrichum Stem Cross Section. Conducting and Support Cells are typically found in the Central Strand. Cross Section of a Polytrichum Leaf. Note the specialized Photosynthetic Parenchyma that has a lot of intercellular air spaces.