Read about Fabaceae in the Standard Cyclopedia of Horticulture
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Laburnum (ancient Latin name). Leguminosae. Including Podocytisus. Golden-chain. Ornamental trees or shrubs chiefly grown for their showy racemes of yellow flowers. Deciduous: lvs. alternate, petioled, 3-foliolate, without stipules: fls. slender-pedicelled, in terminal simple racemes, mostly pendulous; calyx 2- lipped, with obtuse, short lips; corolla papilionaceous, with the petals all distinct; stamens 10, all connate; ovary stalked: fr. a linear pod with several seeds, compressed, tardily dehiscent; seed without appendage at base.—Three species in S. Eu. and W. Asia, often included under Cytisus. All parts of the plants are poisonous, especially the young frs. The hard, tough and closegrained wood is susceptible of a very fine polish, and is manufactured into various small articles. The golden-chains are handsome small trees with dark green trifoliolate leaves falling late in autumn without change of color, and with drooping racemes of bright yellow flowers in late spring, followed by long narrow pods remaining on the tree a long time. They are adapted for planting on rocky slopes or in borders of shrubberies, where they should be allowed enough space to show to the best advantage their graceful, drooping racemes of golden flowers, which contrast with the dark green foliage. They are hardly ever attacked by insects or fungi.—Laburnum alpinum is the hardiest species and perfectly hardy as far north as Massachusetts; L. anagyroides is somewhat less hardy, while L. caramanicum is tender. They thrive in any kind of well- drained soil, including limestone, and grow as well in partly shaded positions as in sunny ones. Propagated by seeds, sown usually in spring, and also by layers; the varieties are mostly grafted or budded on seedlings of one of the species. Laburnum anagyroides, Medikus (L. vulgare, Griseb. Cytisus Laburnum, Linn.). Golden- Chain. Bean-tree. Fig. 2053. Large shrub or small tree, to 20 ft., with erect or spreading branches: branchlets appressed - pubescent, grayish green: lvs. long-petioled; lfts. elliptic or ellipticovate, usually obtuse and mucronulate, glaucous - green and appressed - silky pubescent beneath when young, 1-1 3/4 in. long: racemes silky-pubescent, 4-8 in. long; fls. about 3/4 in. long: pod appressed - pubescent, with thick keel, about 2 in. long; seeds black. May, June. S. Eu. Gn. 25, p. 518; 34, p. 30, and 51, p. 302. G.C. III. 36:318. H. W. 3, p. 101.—There are many garden forms. Var. aureum, Rehd. (var. chrysophyllum, Schneid.), with yellow foliage. F.S. 21:2242, 2243. F. M. 1875: 182. G.Z. 20:129. Var. bullatum, Schneid. (var. involutum, Hort.), with curled lfts. Var. Carlieri, Schneid. (L. vulgare Carlieri, Kirchn.). Lvs. smaller: fls. smaller in short upright racemes, often several from one bud. Var. pendulum, Rehd., with pendulous branches. Gn. 25, p. 522. G.M. 45:317. Var. quercifolium, Schneid., with sinuately lobed lfts. Gn. 25, p. 520; 34, p. 30. Var. sessilifolium, Schneid., with crowded, sessile lvs. Var. Alschingeri, Schneid. (L.Alschingeri, Koch). Racemes shorter, lower lip of calyx longer than upper lip: lvs. more silky. S. E. Eu. Var. autumnale, Rehd. (L. vulgare autumnale, Kirchn. L. vulgare bifera, Lavalle. L. vulgare, semperflorens, Nichols.). Blooms a second time in late summer. Laburnum alpinum, Griseb. (Cytisus alpinus, Mill.). Scotch Laburnum. Shrub or tree, to 30 ft., similar to the former: branchlets glabrous or hirsute when young: lfts. usually elliptic, acute, light green and glabrous beneath or sparingly hirsute, ciliate, 1-1 3/4 in. long: racemes long and slender, glabrous or sparingly hirsute; fls. smaller: pod thin, with the upper suture winged, glabrous; seed brown. June. Mountains, S. Eu. B.M. 176 (as Cytisus Laburnum). Gn. 25, p. 519; 34, p. 30. R.H. 1912, p. 446. G.M. 45:316. G. 36:477. Var. pendulum, Koch. With pendulous branches. Gn. 25, p. 522. A var. aureum is advertised.—This species flowers about 2 weeks later than the former, and has much longer and more slender racemes; it also is of more upright and stiffer growth and hardier. Laburnum watereri, Dipp. (L. Parksii, Hort. C. alpinus x C. vulgaris, Wittst.). Hybrid of garden origin, but found also wild. Lvs. beneath and racemes sparingly pubescent: racemes long and slender: pod with narrow wing, sparingly appressed-pubescent, few-seeded. G.24:355. G. M. 45:313.—As hardy as L. alpinum and sometimes considered to be a variety of that species. Laburnum adamii, Kirchn. (C. Adamii, Poir. C. Laburnum purpurascens, Loud. Laburnocytisus Adamii, Schneid. L. vulgare x Cytisus purpureus). Originated at Vitry, near Paris, about 1826. Habit and foliage usually almost like L. anagyroides, but fls. dull purplish, rarely yellow; sometimes bearing a few branches with the fls. and lvs. of Cytisus purpureus. A very interesting form, but of less ornamental value. B.R. 1965. B.H. 21:16-18. G.C. III. 36:219; 50: 162.—One of the so- called graft-hybrids which have recently been termed chimaeras, as there is no fusion of cell-contents and nuclei, but only a mixture of tissues. L. caramanicum, Benth. & Hook. (Podocytisus caramanicus. Boiss.). Erect shrub, to 4 ft., much resembling in foliage and habit the Cytisus sessilifolius, with long and slender terminal upright racemes. July-Sept. Asia Minor. R.H. 1861, p. 410. G.C. III. 48:454. B.M. 7898.—L. fragarans. Griseb., L. ramentaceum, Koch, and L. Weldeni, Lavalie.—Petteria ramentacea.
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| GRIN-CA 2002-09-01 |
Fabaceae is the botanical name of a large and economically important family of flowering plants, which includes the plants commonly known as legumes. In its broadest circumscription, used here, the Fabaceae sensu lato, also known by the acceptable alternative name Leguminosae, is the third largest family of flowering plants (after Asteraceae and Orchidaceae) with 650 genera and over 18,000 species. These are commonly called legumes or pulses and the family contains some of our most valuable food crops, such as beans, peas, peanuts, soybeans, and lentils. Other members of the family are important sources of animal feed or green manure, such as lupins, clover, alfalfa, cassia, and soybean. Some genera such as Laburnum, Robinia, Gleditsia, Acacia, Mimosa, and Delonix are ornamental trees and shrubs. Still other members of the family have medicinal or insecticidal properties (for instance Derris) or yield important substances like gum arabic, tannin, dyes, or resins.
Some plants of this family are important pests. For example, Pueraria lobata (kudzu), an east Asian species originally planted in the U.S. southeast for soil improvement and as a cattle feed, has there become extremely invasive.
All members of this family have five-petaled flowers in which the superior ovary ripens to form a "pod", technically called a legume, whose two sides split apart, releasing the seeds which are attached to one or both seams.
According to the classification system being consulted, the name "Fabaceae" can have one of two different meanings:
- As used here, it can refer to a large family, Fabaceae sensu lato, which consists of three subfamilies, Mimosoideae, Caesalpinioideae, and Faboideae (often called Papilionoideae). The International Code of Botanical Nomenclature allows the use of Leguminosae as an equivalent botanical name to this larger family. This meaning is used by the APG system and many floras.
- Alternatively, it can refer to the subfamily Faboideae treated at the family level. In this circumscription, the other two subfamilies become the families Mimosaceae and Caesalpiniaceae. This circumscription is used in the Cronquist system and elsewhere. The smaller Fabaceae in this system can be referred to as "Papilionaceae", a name also approved by International Code of Botanical Nomenclature.
In consulting any reference that uses the name Fabaceae, care should be taken to make sure what group it applies to.
Subfamilies
The Fabaceae are traditionally classified into three subfamilies (raised in the alternate classification to the rank of family in the order Fabales), on the basis of flower morphology (specifically, petal shape):
- Caesalpinioideae (Caesalpiniaceae): The flowers are zygomorphic, but are very variable, e.g. closely resembling Faboideae flowers in Cercis, while symmetrical with five equal petals in Bauhinia.
- Mimosoideae (Mimosaceae): The petals are small, and are frequently globose or spicate and the stamens a
re the most showy part of the flower.
- Faboideae or Papilionoideae (Fabaceae sensu strictu or Papilionaceae): One petal (the banner) is large and has a crease in it, the two adjacent petals (wings) are on the sides, and the two bottom petals are joined together at the bottom, forming a boat-like structure (keel).
Nitrogen fixation
A significant characteristic of legumes is that they host bacteria in their roots, within structures called root nodules. These bacteria known as rhizobia have the ability to take nitrogen gas (N2) out of the air and convert it to a form of nitrogen that is usable to the host plant ( NO3- or NH3). This process is called nitrogen fixation. The legume, acting as a host; and rhizobia, acting as a provider of usable nitrate, form a symbiotic relationship.