Pollen grains often have air bladders, or vesicles, called sacci. The sacci are not actually balloons, but are sponge-like, and increase the buoyancy of the pollen grain and help keep it aloft in the wind, as most gymnosperms are anemophilous. Pollen can be monosaccate, (containing one saccus) or bisaccate (containing two sacci). Modern pine, spruce, and yellowwood trees all produce saccate pollen. The transfer of pollen grains to the female reproductive structure (pistil in angiosperms) is called pollination. This transfer can be mediated by the wind, in which case the plant is described as anemophilous (literally wind-loving). Anemophilous plants typically produce
Coating substrate, such as paper, fabric, film, foil, or sheet stock. If the substrate starts and ends the process wound up in a roll, the process may be termed "roll-to-roll" or "web-based" coating. A roll of substrate, when wound through the coating machine, is typically called a web. Coatings may be applied as liquids, gases or solids. Coating processes may be classified as follows: Common roll-to-roll coating processes include: Coating A coating is a covering that is applied to the surface of an object, usually referred to as the substrate. The purpose of applying the coating may be decorative, functional, or