Fern relations: a patch of forest in Massachusetts harbors some shady characters

Natural History, Oct, 2003 by Robert H. Mohlenbrock

Near the foot of the Berkshire Hills, alongside the scenic Housatonic River in southwestern Massachusetts, is a National Natural Landmark known as Bartholomew's Cobble. In its 329 acres more than 800 plant species flourish, including fifty-three species of ferns and so-called fern allies, one of the finest such concentrations in the United States. The "Cobble" part of the site's name refers to two large, adjacent outcroppings of bedrock (think "cobblestone"). Bartholomew is the name of a family that farmed the land from 1833 until 1901. The Trustees of Reservations, a Massachusetts land trust that now owns the property, acquired the main parcel in 1946 and added to it in subsequent years through purchases and donations.

About 70 percent of the landmark area is covered in forest dominated by hemlock. Where the shade is not too dense, the forest floor is brightened by a number of flowers, especially in springtime; in autumn, broadleaved trees such as northern red oak and sugar maple stand out amid the evergreens, adding splashes of blazing red and orange. Portions of the rock outcroppings are also forested with hemlocks or other trees, and many plants find a foothold in the crevices of the exposed bedrock. Only the west-facing areas of the limestone, marble, and quartz, which get the brunt of the afternoon sunshine, remain dry and nearly bare of vegetation.

Found in the shade throughout the growing season are numerous ferns and fern allies. All of them are vascular plants that do not form seeds as part of their reproductive cycle. Like many plants, their generations alternate between a spore-producing form, called the sporophyte, and a gamete-producing form, called the gametophyte. In vascular plants, the sporophyte is the plant people usually see and recognize. It gives rise to spores, which are haploid cells--cells that contain only one from each pair of chromosomes in the parent plant. The dispersed spores grow into gametophytes, small and obscure structures that give rise to gametes, or sex cells. When two gametes unite-restoring the double number of chromosomes--the resulting cell can give rise to a new sporophyte. (A seed is merely a dormant, embryonic sporophyte, protected by a covering and supplied with a store of food; dispersed in this form, the sporophyte can germinate and grow rapidly when conditions are right.)

Ferns, whose sporophytes usually have delicate-looking, much divided, broad, flat leaves, are common denizens of the forest. About forty-five species grow at Batholomew's Cobble. Fern allies tend to be less familiar. They often differ from ferns in the appearance of their sporophytes but are defined botanically according to various details of their gametophyte life cycle, which is more complicated than that in ferns.

Fern allies fall into five families, three of which are represented in the landmark area. One of these is the Equisetaceae, members of which are often referred to as living fossils: the group dominated terrestrial plant life when dinosaurs roamed the Earth. Their sporophyte has a jointed, leafless stem containing silica, which the plant takes up from the soil. If the stem is unbranched, the species is aptly (but not always) called a scouring rush (American pioneers would bind bunches of the stems together and use them to scour pots and pans). If whorls of very slender branches radiate from each joint, making for a bushy-looking plant, it is more appropriately referred to as a horsetail.

Two more families of fern allies found in Bartholomew's Cobble are the club mosses (Lycopodiaceae) and spike mosses (Selaginellaceae). Both tend to have small leaves that are flat or scalelike. Club mosses with stiff branches and scalelike leaves are often called ground pines.

HABITATS

Hemlock forest American beech, basswood, northern red oak, sugar maple, and white pine, along with the hemlock trees, create a deep shade. In it grow such ferns as adder's-tongue fern, bog fern, Christmas fern, crested fern, Goldie's fern, maidenhair fern, New York fern, ostrich fern, and spinulose woodfern. The delicately branched woodland horsetail and two ground pines (fan club moss and running club moss) also grow here. Where the woods border the Housatonic River appear colonies of large cinnamon fern, ostrich fern, and royal fern, along with the somewhat smaller sensitive fern. Joining these are three scouring rushes (common scouring rush, variegated scouring rush, and water horsetail) and the common, or field, horsetail.

Wildflowers that grow beneath the canopy include so-called spring ephemerals--plants that usually come up in early April, bloom no later than the end of May, set seeds in May or June, and disappear by July. Among them are Dutchman's-breeches, spring-beauty, and various species of toothwort, trillium, and violet. A few spring wildflowers persist, such as doll's-eyes, Solomon's seal, and false Solomon's seal. Nonephemerals that bloom during the summer or fall are Canada lily, false hellebore, and species of aster, goldenrod, and sunflower.