Dawsonia (plant) lamella – chains of small cells on the upper surface of the leaves analogous to the mesophyll cells of vascular plant leaves. They increase the surface area of cell walls available for CO uptake, while at the same time maintaining layers of moist air between lamellae, reducing water loss. Lamella margins have a surface wax layer which prevents water from flooding into the interlamellar spaces. Dawsonia (plant) Dawsonia is a genus of acrocarpous mosses. "Dawsonia", along with other members of the order Polytrichales, are taller than most mosses and have thicker leaves. Their sporophytes have conducting systems analogous to those
Mastoid cells is not pneumatized, but becomes aerated over the first year of life. Poor pneumatization is associated with eustachian tube dysfunction. Infections in the middle ear can easily spread into the mastoid area via the aditus ad antrum and mastoid antrum. Mastoid cells A section of the mastoid process of the temporal bone of the cranium shows it to be hollowed out into a number of spaces, the mastoid cells, which exhibit great variety in their size and number. At the upper and front part of the process they are large and irregular and contain air (a form of skeletal pneumaticity),