Fruits. A true fruit is a ripened ovary, bearing one or more ripened ovules, the seeds. The wall of the fruit, developed from the wall of the ovary, is called the pericarp. This pericarp may be fleshy, relatively soft and juicy, or dry, relatively hard and tough; of course all sorts of gradations exist between these two types.
Fruits are quite often present on woody plants in winter. These are most likely to be dry fruits, since fleshy fruits are more perishable and are likely to have fallen and rotted, or to have been eaten by animals, particularly birds. Those fleshy fruits which do persist until winter are likely to have withered, as the coralberry, or to be fruits with scanty pulp, as the hackberry.
Of fleshy fruits present in winter, one of the most common is the drupe (Fig. 21). This has the pericarp consisting of three distinct layers, the exocarp, mesocarp, and endocarp, the endo-carp taking the form of a hard stone surrounding the seed; fruits of this type are often called "stone fruits". Examples are black haw and hackberry. Drupes are usually considered as one-seeded, but in some instances, as in holly, several stones (endocarps), each with its own seed, may be surrounded by the same mesocarp. The pome (Fig. 22) is developed from a several-carpelled, several-seeded inferior ovary, the fleshy portion being a combination of pericarp and and roperianth tube (a tube composed of the coalesced lower portions of the sepals, petals, and stamens); examples are hawthorn, chokeberry, and mountain-ash. The rose hip (Fig. 23) is an aggregate fruit, having many separate carpels of a single flower within the fleshy, hollowed-out receptacle.
Dry fruits include the legume (e.g., redbud), a fruit with one locule but splitting along two sutures (Fig. 24); the follicle (e.g. ,ninebark), like a legume but splitting along one suture only; (Fig. 25); and the capsule (e. g., catalpa), a dry fruit of two or more carpels, splitting into each locule (Fig. 26). All these may be classed as dehiscent (opening to permit the escape of numerous seeds). Other dry fruits are indehiscent containing but one seed and therefore not needing to open, since the entire fruit functions as a single seed. Among dry indehiscent fruits are the achene, a small fruit with the pericarp closely investing the seed (e. g., sycamore, with the many achenes compounded to form a globose head); the samara (Figs. 27, 28, 29), like an achene but provided with a wing which favors wind dispersal (e. g., elm, hoptree); and the nut (Figs. 30, 31),like an achene but larger, with a hard leathery or bony pericarp (e.g., chestnut, beech). A special type of a nut is the acorn of oaks, where the nut proper is borne in a cup representing a modified involucre (Fig. 32). In walnut and hickory the nut has some of the properties of a drupe, with an exocarp and a mesocarp (the husk) separating from the hard bony endocarp (the shell); such a fruit has been called a tryma (Fig. 33).
Very few woody plants produce their flowers during the winter months. Witch-hazel, the only fall-blooming shrub in our region, sometimes has its yellow flowers persisting until winter (Fig. 38). Most winter-blooming plants, however, are in reality pre-vernal (early spring) in nature, coming into bloom in late February or March, and usually persisting into spring (or in the event of unusually sustained cold weather, not beginning to bloom until spring). Examples are willows, elms, and maples (Figs. 34,35,36,37,39).