Trafficking of nutrients: satisfying nutritional requirements of spatially separated shoot and root systems. Root system for assimilation of water and mineral ions. Vertical growth: support of shoot in a non-viscous aerial environment. Lignified cellulose cell walls confers mechanical strength to position photosynthetic organs to intercept incident solar radiation. Water loss: large photosynthetic surfaces are vulnerable to water loss by evaporation. Stomata - hydraulically operated pores to regulate gas exchange. Water loss during reproduction: desiccation of gametes and embryos. Gametangia - specialized structures to produce and protect gametes and embryo resulting from internal fertilization. Pollen - water impermeable delivery system to transfer sperm for cross fertilization independent of a requirement for water. Seed - embryo contained within a protective covering for dispersal. Dispersal of pollen and seed: seed and pollen dispersal aids cross- pollination and increases geographic spread. Flower pollen dispersal by wind (grasses) and animals (remainder) increases probability of fertilization. Fruit - maternal tissues encasing the seed enhanced dispersal.