Passion Flower (Passiflora), a genus of plants so named because the early Spanish missionaries regarded them as emblematic of the passion or crucifixion of Christ and its attendant circumstances. It contains about 120 species of mostly climbing, herbaceous, or woody plants, all of which, save a few in Asia and Australia, belong to the American continent, especially to the tropical portions. Five species are found in the Atlantic states, one extending as far north as Pennsylvania and Illinois. In some species the flowers are large and showy, and among the most brilliant of the occupants of our plant houses; in others they are small and inconspicuous; and in all the structure is striking and peculiar. The leaves in some are remarkable for their form or markings, several species being cultivated for their foliage only; the leaves, generally alternate, are entire or variously lobed or parted, with petioles which are often furnished with glands, and with or without stipules; the tendrils by which the plants climb are rarely wanting, and, being mostly axillary, are regarded as abortive flower stalks, as it is not rare to find them bearing flower buds. The flowers are axillary- and solitary, or in racemes, the flower stalk or pedicel usually bearing three leafy bracts embracing the base of the flower.
The structure of the flower, which is much out of the ordinary way, will be best understood by aid of a longitudinal section, as given in the engraving. The calyx consists usually of five sepals, united below to form a short cup or tube; the free expanded portion is colored like the petals within, or on the upper side, and often having on the outside, just below the tip, a small hook or claw. The petals are usually five, sometimes wanting, attached to the throat of the calyx tube, and with them is inserted a series of thread-like processes in two or more rows, forming a compound fringe, called the crown or ray; to this the great beauty of most of these flowers is chiefly due, as aside from the unusual appearance it imparts, sometimes extending beyond the petals, and again quite short, it is often beautifully colored and marked, frequently in contrast with the color of the rest of the flower; the real nature of these filaments has been much discussed, but Dr. M. T. Masters, who has given special study to the family, regards them as abortive stamens, a view confirmed by the structure in related gen-•era. The stamens are of the same number as the calyx divisions and opposite them; their filaments are united below to form a tube sheathing, and more or less united to the stalk which supports the pistil, but distinct above, their free portions widely spreading and terminated by large oblong anthers hung by the middle.
In the centre of the flower arises a stalk or column (gynophore), which is a prolongation of the receptacle and bears at its apex the pistil, consisting of a one-celled ovary, with three club-shaped styles, terminated by large button-like stigmas. The fruit is a berry, with a more or less hard rind, pulpy within, and containing numerous seeds on three parietal placentae, each seed surrounded by a pulpy covering (ai'illusj; the fruit in many species is edible. From this outline of the structure, the origin of the name passion flower will be understood; in the palmate leaves of the plant are seen the hands of Christ's persecutors, and in the conspicuous tendrils the scourges; the ten parts of the flower envelope, calyx and corolla together, stand for the disciples, two of whom, Peter and Judas, were absent; the fringe represents the crown of thorns, or according to some the halo of glory; the five anthers are symbolic of the five wounds, and the three styles with their capitate stigmas stand for the nails, two for the hands and one for the feet, with which the body was nailed to the cross. - The showiest of our native species, passiflora incarnata, is found as far north as Kentucky and Virginia, and is especially abundant further south, where it often remains in cultivated land as a weed; its stems, trailing on the ground or climbing upon corn and other crops, are regarded as troublesome; it has a perennial root, and spreads widely by means of underground stems; its leaves are three-cleft, and the flower, 2 to 3 in. broad, pale purple or nearly white, with a purple or sometimes flesh-colored crown, is sufficiently handsome for cultivation; the fruit, known throughout the southern states as "maypops," is about the size of a hen's egg, dull yellow when ripe, and edible; an extract of the leaves and an infusion of the root have been used medicinally, particularly as a vermifuge.
This species, especially if the roots are covered with litter during winter, is sometimes hardy in northern gardens, and is a fine vine for a low trellis, though its running under ground makes it troublesome, as the shoots in spring will often appear a yard or two away from the place where the plant stood the season before. The yellow passion flower (P. lutea), growing as far north as Pennsylvania and Illinois, is a smaller plant, and its greenish yellow flowers, scarcely an inch across, are more interesting than beautiful. Our other three species, natives of Florida, are not showy or of any known use. P. suberosa has greenish yellow flowers and small purple fruit; P. angustifolia has yellowish flowers half an inch across, and fruit the size of a pea; and P. Warei is equally insignificant in appearance. The commonest exotic species is the blue passion flower (P. cce-rulea) from South America, which has been in cultivation for nearly two centuries; it is hardy in parts of England and on the European continent, but not in our northern states; it is cultivated in cool greenhouses, and treated as a bedding plant; if planted out in warm weather, it grows very rapidly and produces a profusion of its handsome flowers, which are very pale blue, with a purple centre and a blue crown, which has a white band in the middle.
Passion Flower, longitudinal section.
1. Seed surrounded by aril. 2. Transverse section of ovary.
Blue Passion Flower (Passiflora caeralea).
Something over 100 named passion flowers are in cultivation, including hybrids and varieties from seed; of these only a few of the more common and striking can be noticed. The edible passion flower (P. edulis), called with several others granadilla, is a very old greenhouse plant, and, where climbers are desired, useful for its rapid growth, dark green abundant foliage, and numerous white and blue, sweet-scented flowers; its purple fruit, the size of a goose egg, is esteemed for dessert. (See Granadilla.) The winged (P. alata) and the four-angled (P. quadrangular is) passion flowers both have four-sided branches, the angles of which are winged; both are free-flowering stove climbers, with large, sweet-scented, red or crimson flowers, in which the crown is variously colored; the two species differ in the structure of the crown, and the last named, called the large granadilla, has an edible fruit 6 or 8 in. in diameter; a variety, P. Decaisneana, with larger and more showy flowers than either, is supposed to be a hybrid between these two. The large-fruited passion flower (P. macro-carpa) has fruited in England, producing enormous berries weighing as much as 10 lbs. each.
Among the other choice species and varieties in cultivation are P. princeps, Buonapartea, Tcermesina, coccinea, sanguinolenta, and circin-nata, the last named remarkable for the very long and slender wavy rays to the crown. Among those cultivated for their beauty of foliage is P. trifasciata, in which the dark olive-green leaves have three broad bands of greenish white corresponding to their three lobes, but the flowers are small and not showy. A few species are annuals; among them P. gracilis, remarkable for the rapidity of the movements of its tendrils, is one of the species observed by Darwin in studying the movements of climbing plants; the internode carrying the upper tendril made six revolutions at an average of 1 h. 1 nu; a single touch near the tip of a tendril wheii in its most sensitive condition caused it to curve, and in two minutes it formed an open helix. The genus tac-sonia (from tacso, the Peruvian name for the plants) differs from passiflora chiefly in having a long calyx tube, often over 3 in. long; their habit of growth is similar, and their flowers often exceedingly brilliant; their horticultural uses are identical with those of the passion flowers. - In cultivation at least, some passion flowers are singularly self-sterile; though an abundance of active pollen is produced, this will not fertilize the pistils on the same plant, but it will those on a different species, and the pistils which refuse to accept their own pollen readily become impregnated by that from another species.
P. racemosa, c&rulea, and alata, in the botanic garden at Edinburgh, refused for many years to bear fruit, though the flowers of each frequently had their own pollen applied to them artificially; but when these three were crossed in various ways with the pollen of either of the others, fruit was abundantly produced. It is probable that this state of things does not exist among these plants in the wild state, but that, as the reproductive function is often affected by slight external eauses, self-sterility in these plants has been induced by the unnatural conditions of cultivation. This view is supported by the fact that P. alata in some greenhouses is inveter-ately self-sterile, while in other places it fruits abundantly by the aid of its own pollen; and a plant known to be self-sterile was by grafting upon another species rendered ever afterward self-fertile. But little is certainly known about the medicinal qualities of the passion flowers; the roots and leaves of several are employed in their native countries as expectorants, narcotics, and anthelmintics; the root of one of the granadillas, P. quadrangularis, very common in greenhouses, is said to be diuretic, emetic, and so powerfully narcotic as to be regarded as poisonous. - Passion flowers are increased with the greatest ease from cuttings of the young wood, and they may also be raised from seeds.
If the plants are not set in the ground of the greenhouse, they should have very large pots or boxes, as the roots require much room.