Page:Popular Science Monthly Volume 80.djvu/232

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rushes, sedges and salt-grasses. Frequently even the beach, many feet back from the water's edge, is so thoroughly impregnated with salts that they crystallize and form a white crust over the surface. This results in an absolutely barren zone. Back of that portion of the beach washed by the waves the salt-enduring plants develop very copiously. The saltgrass (Distichlis spicata) is usually controlling in such places where the low plants develop a very close tenacious sod. Beyond the belt of saltgrasses the taller stems of other grasses, sedges and rushes make up another distinct zone which may completely encircle the pond or lake. These plants are very dark green, so that the belts of vegetation about the saline lakes stand in marked contrast to the duller tones of the surrounding hills. Still farther back beyond the zone of tall plants the shore vegetation of the saline lake passes either abruptly or gradually into the typical wet meadow vegetation.

The appearance of the fresh-water lakes is quite different. First of all there is usually a wealth of submerged or half-submerged plants. Some of these lakes are literally filled with great masses of pondweeds (Potamogeton, several species), and the water milfoil (Myriophyllum spicatum). The bottom, in the shallower portions of such lakes, is covered with a carpet of stonewort (Chara fœtida, etc.), while the stems of the submerged flowering plants are richly coated with algae of many kinds. In late summer certain of these algæ become broken away from their substrata and float about on the surface of the water. During high winds at this time great quantities of these, such as the net sack (Clathrocystis æruginosa), are washed on the beach in yellow green splashes. So there are many very interesting animals in the freshwater lakes, a sponge being one of the common forms.

The white, encrusted beach is absent from the fresh-water lakes, as also are the belts of salt-enduring plants. The commonest marginal plant here is the great bulrush (Scirpus lacustris). Frequently this is the only plant between the bunch-grass association of the hills and the open water of the lake. Sometimes other species such as cat tail (Typha latifolia), and the giant reed grass (Phragmites phragmites) occur in mixture with the bulrush, or these may now and then form separate belts. Wild rice grass (Zizania aquatica) is a common marginal or shallow-water inhabitant of many of the lakes. This plant is about as tall as the bulrush, but because of its leafy stems it often forms much denser stands in the shallow water. When the seed is ripe every bed of wild rice is a Mecca for thousands of water fowl that live in the vicinity of the lakes. Wild ducks become so thick at times in these rich feeding grounds that the noise they make reminds one of an over-stocked barnyard.

The lakes range in size from small ponds to bodies of water one and