PLANT ADAPTATIONS
Any plant that is adjusted to living in a region where there is a decided lack of water is called a “xerophyte.” There are many different ways in which plants have adapted their structure and way of life to the dune environment. For instance, to reduce water evaporation they may have a very small leaf, to offer less surface area to the sun; or smaller and more numerous stomata than other plants (“Stomata” are tiny openings through which plants exchange gasses. A pair of guard cells surround them and control the size of their opening); or a very thick cuticle (waxy protective covering found on many plants); or their sap may be changed chemically. Xerophytes may also be very fleshy, like the cactus, to give more storage space for water. Their roots may drive very deep into the ground to reach the water table, or they may be shallow and spread out over a wide area to cover more surface. Their leaves may grow in closely packed bundles to reduce further the surface area, or they may be very thorny and prickly as a protection in exposed surroundings.
Here are just a few common examples of xerophytes and other plant adaptations to be found at Crane’s Beach.
Anchor for the Dunes
Beach Grass (Ammophila breviligulata) is a true xerophyte and has many sand-dwelling characteristics. Its grasslike blade is rolled in at the sides, oftentimes becoming a tube, in order to reduce the surface area. As you will probably discover, it has a pointed tip that can prick a finger and, as you may well imagine, acts as a deterrent to those who would eat or walk through it. Its underground stems, in true xerophyte fashion, extend over a large area in an attempt to gather all possible water, and these dense root-mats serve to anchor the dunes and prevent their migration.
A Tough Sand Dweller
The Woolly Hudsonia (Hudsonia tomentosa) carpets the dunes, preferring its place in full sun to more shaded spots. The tiny leaves are awl-shaped and press very tightly against the stem, as though trying to hold in as much water as possible. Hudsonia is covered with a velvet-like down, which is less susceptible to evaporation than a smooth, large surface would be.
An Adaptable Mushroom
Since mushrooms generally require plenty of water, you would not expect to find them at the beach. Several species, however, may be discovered here. The most readily identifiable is the Earth Star (Geaster hygrometricus), which resembles a Puff Ball but differs in having the outer layer of the skin divided into tough, star-shaped segments. During the dry seasons, this star is drawn up around the ball by its contraction, thus protecting it against further desiccation. In wet weather, the ball swells and holds the star against the ground to allow for water absorption. The “roots” of the Earth Star are shallow, so the plant may readily be dislodged. The wind easily blows it across the dunes, spreading the spores over a wide area.