In the Bryophytes water is still absorbed, not only from the soil but also largely from rain, dew, &c., through the general surface of the subaerial body (thallus), or in the more differentiated forms through the leaves.
Terrestrial plants have a gaseous interchange of oxygen and carbon dioxide which is necessary for respiration and feeding.
This surface layer in the typically subaerial shoot of the sporophyte in Pteridophytes and Phanerogams is known as the epidermis, though the name is restricted by some writers, on account of developmental differences, to the surface layer of the shoot of Angiosperms, and by others extended to the surface layer of the whole plant in both these groups.
Geomorphology is the part of geography which deals with terrestrial relief, including the submarine as well as the subaerial portions of the crust.
Being protected by the water from the rapid subaerial erosion which sharpens the features of the land, and subjected to the regular accumulation of deposits, the whole ocean floor has assumed some approach to uniformity.
' In some localities it is not easy to establish irrefutably and in detail the inter-arrangement of drainage and rock structure that proves it to be a subaerial peneplain instead of an uplifted submarine platform; but the general proof is very clear.
Produced by long-continued subaerial decay and erosion, in later Cretaceous times this lowland extended from the Atlantic Ocean well toward the interior of North America; since then the whole continent has been generally elevated, and by successive steps the Appalachian belt has been raised to form a wide but relatively low arch.
The fourth period is that in which the various subaerial agencies of abrasion, and especially the streams which drain the mountain chain of the Apennines, have produced the present features of the Campagna, a plain furrowed by gullies and ravines.
The presence of these fossils indicates that the eruptions were subaerial, and a comparison of them with those elsewhere found among Older Tertiary strata shows that they probably belong to the Oligocene stage of the Tertiary series of formations, and therefore that the basalt eruptions took place in early Tertiary time.
A terrestrial habitat is less common, but the widely-distributed land Isopoda or woodlice and the land-crabs of tropical regions have solved the problem of adaptation to a subaerial life.