The New Student's Reference Work/Hydrophytes
Hy′drophytes. The name literally means water-plants. The water conditions in which such plants grow range from complete submergence to swamps. Such plants have various adaptations for living in connection with a large amount of water. If the plant lives submerged, there is a feeble development of the tissues for mechanical support, and when it is removed from the water it collapses. Another common adaptation of water-plants, found also in swamp forms, is the development of conspicuous air-passages for aeration. Stalks of water-lilies, calladiums etc. easily show these large passageways. It is necessary for air to be brought into the plant and carried to parts which are too much shut off from air by water. In certain plants which float, bladder-like floats are provided, as in the common bladderworts. There are three conspicuous types of hydrophytes. The first type is made up of the “free floating societies,” that is, those in which the plants are entirely sustained by water and are free to move either by locomotion or water currents. To this group belong the ordinary pond societies, composed of algae, duckweeds etc., which float in stagnant or slow-moving water. The second type is made up of the “pondweed societies,” in which the plants are anchored, but their bodies are submerged or floating. Here belong the associations of seaweeds, among which there are often elaborate systems of holdfasts. Another conspicuous pondweed society is that which contains among its representatives the water lilies with their broad floating leaves and the pondweeds or pickerel weeds with entirely submerged leaves. The third type is made up of “swamp societies,” in which the plants are rooted in water or in soil rich in water, but the leaf-bearing stems rise above the surface. The conspicuous swamp societies are “reed swamps,” characterized by tall rushes, cat-tails and reed grasses, wand-like monocotyledons which usually form a fringe about shallow margins of small lakes and ponds; “swamp moors,” the ordinary swamps, bogs, marshes etc., which are covered by coarse grass; “swamp thickets,” in which there is a tangle of willows, alders etc.; “sphagnum moors,” in which the sphagnum moss prevails and is accompanied by numerous orchids, heaths etc.; “swamp forests,” in which the tamarack (larch), spruce, pine, hemlock and juniper are the prevailing trees.