AP BIOLOGY

Detailed explanation-1: -You can see that the leaf is largely one cell thick, but there is a clear thickening (the nerve) in the centre. The nerveless part of the leaf is about a hundredth of a millimetre thick. While moss leaves are, apart from a nerve, generally one cell thick there are some exceptions, such as the genus Leucobryum.

Detailed explanation-2: -The phyllids are usually attached by an expanded base and are mainly one cell thick. Many mosses, however, possess one or more midribs several cells in thickness. The phyllids of bryophytes generally lack vascular tissue and are thus not analogous to the true leaves of vascular plants.

Detailed explanation-3: -Spores of bryophytes are generally small, 5–20 micrometres on the average, and usually unicellular, although some spores are multicellular and considerably larger.

Detailed explanation-4: -Mosses typically form dense green clumps or mats, often in damp or shady locations. The individual plants are usually composed of simple leaves that are generally only one cell thick, attached to a stem that may be branched or unbranched and has only a limited role in conducting water and nutrients.