Water

• A handful of plant species took the opposite tack from the majority of the kingdom, which evolved to decrease its dependence on water. About 2 percent of flowering plants occupy aquatic environments, and fewer than 130 aquatic plants --- primarily seagrasses and pondweeds --- use water to carry their pollen, a phenomenon called hydrophily. Pollen may float on the surface or drift underwater from plant to plant. The majority of plants that use hydrophily have separate male and female flowers, which may help these plants achieve genetic diversity.
  
  

Wind

• Although they're technically flowering plants, grasses don't produce colorful flowers.Thinkstock/Comstock/Getty Images
  
  More plants use wind than water for pollination, a phenomenon called amenophily. The U.S. Forest Service estimates that approximately 12 percent of the world's plants use the wind to carry their pollen, including the majority of conifers and grasses, as well as deciduous trees such as oak and birch. These plants can release so much pollen that it creates visible clouds or a haze over the landscape. Wind-pollinated plants also account for a lot of pollen-related allergies. The flowers of wind-pollinated plants are easy to overlook. Because they don't have to attract pollinators, they lack the bold colors and sweet scents of many of their relatives. They tend to be small, with the female structures exposed to air currents. Male structures produce an abundance of light, smooth pollen that carries easily on the wind.
  
  

Pollinators

• Hummingbirds can't smell, so the red flowers that attract them usually lack scent.Tom Brakefield/Stockbyte/Getty Images
  
  Other members of the flowering plant division have evolved flowers that attract specific animals, offering the animal a reward of nectar or pollen for food so the animal will carry the pollen from plant to plant. The colors and scents of flowers appeal to particular pollinators. For example, bee-pollinated flowers tend toward the violet end of the color spectrum, since bees can't see red. Some bee-pollinated flowers even include ultraviolet markings that help guide the bee to the nectar source. Red flowers attract hummingbirds, and white flowers attract moths. Scent also plays a role, and while the sweet, heady scent of wild roses might come first to mind when thinking of plant fragrance, some plants have developed less pleasant adaptations to attract pollinators. Carrion plants, for example, smell of rotting meat and attract beetles as pollinators. Night flowers pollinated by moths produce strong scents to help attract the moths in the dark.
  
  

Self-Pollination

• Although far less dramatic than the boldly colored methods employed by their relatives, some flowering plants self-pollinate. Although this doesn't allow the advantage of genetic diversity, it helps plants in climates where pollinators may not be available, allowing plants to conserve the energy they'd usually spend attracting pollinators while guaranteeing a good crop of seed. Self-pollinated flowers contain both male and female structures, and the pollen drops directly from the male to the female parts, sometimes before the bud even fully opens.