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
Vascular plant and transported throughout the plant by the xylem. Organic compounds such as sucrose produced by photosynthesis in leaves are distributed by the phloem sieve tube elements. The xylem consists of vessels in flowering plants and tracheids in other vascular plants, which are dead hard-walled hollow cells arranged to form files of tubes that function in water transport. A tracheid cell wall usually contains the polymer lignin. The phloem however consists of living cells called sieve-tube members. Between the sieve-tube members are sieve plates, which have pores to allow molecules to pass through. Sieve-tube members lack such organs as nuclei or