2752 



PONCIRUS 



PONGAMIA 



Makino. Mglel sepidria, DC. Limdnia? trichocdrpa, 

 Hance. Citrus triptera, Carr.). TRIFOLIATE ORANGE. 

 Figs. 3123-3125. A small tree, spines long and stout: 

 Ivs. deciduous, trifoliolate, often borne in tufts on old 

 wood (see Fig. 3123); terminal Ifts. 1^-2^ in. long, 

 lateral ones 1-2 in. long, sessile, petiole slightly winged: 

 fls. 1^-2 in. across, white, the corolla opening nearly 



3124. Flowers of Poncirus 

 trifoliate. (X 1 A) 



flat, and the petals nar- 

 rowed to a claw at base 

 (Fig. 3124), stamens free, 

 ovary 6-8- (generally 7-) 

 celled: fr. very fragrant, 

 dull lemon-colored, like a 

 small orange in shape, but 

 only 1 J/2-2 in. diam., and 

 covered with fine downy 

 hairs, oil-glands of peel 

 abundant, filled with a very disagreeably flavored oil, pulp 

 scanty, very aromatic, seeds ovoid, plump, very numer- 

 ous, leaving little space for pulp. Illus. Kaempf. 

 Amoen. 801. B.M. 6513. G.C. III. 27:269. Penzig, 

 Studi sugli Agrumi, Atlas, pis. 13, 14. U. S. Dept. Agric. 

 Yearbook 1904, pi. X. U. S. Dept. Agric. B.P.I. Circ. 

 No. 46, figs. 1-^6, pi. 1. Comptes rendus 4 me Confer. 

 Internat. Genet, p. 386. The trifoliate orange has been 

 known in N. China since ancient times, being repeatedly 

 referred to in early works, and it was described and 

 figured in the Chgng lei pen ts'ao, printed in 1108 A.D. 

 It was early intro. into Japan and definitely referred to 

 in the Mannyo shu, a Japanese MSS. work dating 

 from the 8th century. Var. monstrosa, Swingle (Citrus 

 trifoliata var. monstrosa, T. Ito in Encyclopedia Jap- 

 onica, 2:1056). HIRYO, or FLYING DRAGON. This is a 

 curious, very dwarf variety with tortuous branches 

 and curved spines. The Ivs. are very small and incon- 

 spicuous as the Ifts. are often reduced to mere fila- 

 ments on which the oil-glands appear as node-like 

 thickenings. This variety is esteemed in Japan for 

 cult, as a dwarfed pot-plant. The writer introduced it 

 from Japan into this country in 1915. 



The hybrids between Poncirus trifoliate, and the com- 

 mon orange are called citranges. A number of varie- 

 ties, Rusk, Colman, Morton, and so on, are grown for 

 home use in the cotton-belt, north of the limit of suc- 

 cessful orange-culture. See Citrange. Promising hardy 

 hybrids have been made at the Department of Agricul- 

 ture under the writer's direction between P. trifoliata 

 and a number of other species of citrous fruits, such 

 as the sour orange, mandarin, grapefruit, lemon, lime, 

 calamondin, kumquat (Fortunella sp.), and others. 

 These are being tested in the field. 



The principal use of the trifoliate orange is for stock 

 upon which to graft the commonly cultivated citrous 

 fruits. It is especially well adapted to rather rich 

 somewhat moist, sandy loam soils, preferably with a 

 clay subsoil, such as are common around the Gulf 

 Coast. It is not at all adapted to light sandy soils, nor 

 to strongly calcareous soils. Almost all kinds of citrous 



fruits grow readily on trifoliate stock but are dwarfed 

 somewhat and usually forced into early bearing. The 

 Satsuma orange as grown commercially in this country 

 is practically limited to this stock as it does not grow at 

 all on sour orange stock and succeeds only very imper- 

 fectly on sweet orange stock. Trifoliate stock is also 

 very widely used in Japan. In the states south of the 

 Potomac and Ohio rivers the trifoliate orange is some- 

 times used for hedges, for which purpose it is well 

 adapted because of its dwarfed habit, strong thorns, 

 handsome flowers, foliage, and fruits. Even in winter 

 after the leaves have fallen its twigs remain green. It is 

 very widely used for hedges in Japan. P. trifoliata is 

 also of value as an ornamental tree for lawn planting, 

 for which purpose care should be taken to secure large- 

 flowered forms.' It can be grown for this purpose as 

 far north as Philadelphia. The trifoliate orange shows 

 surprisingly little variation. Millions of seedlings are 

 grown every year in the larger citrous nurseries of this 

 country but it is rare to see any perceptible variation 

 in the character of the leaves and twigs. The flowers, 

 however, do show variation, often having a partial 

 staminody of the petals (rarely complete) which makes 

 them smaller and less handsome than the normal large 

 flowers. The fruits are usually nearly spherical but 

 rarely are somewhat elongate and papillate, much like 

 a very small lemon. WALTER T. SWINGLE. 



POND-APPLE: Annona glabra. P. Lily: Nuphar. P.-weed: 

 Potamogeton. 



PONGAMIA (a native Malayan name). Legumi- 

 nosse. A single arborescent or shrubby species of tropi- 

 cal Asia and Australia, little known in this country. 



Leaves odd-pinnate; Ifts. opposite: fls. racemed; 

 calyx campanulate, nearly truncate; corolla much 

 exserted; standard broad; keel obtuse, the petals 

 cohering at the tip; stamens monadelphous, the upper 

 filament free low down; anthers oblong, versatile; 

 ovary subsessile, 2-ovuled; style incurved, glabrous; 

 stigma capitate: pod flattened, oblong, indehiscent, not 

 at all winged or thickened at the sutures. It is related 



3125. Poncirus trifoliata. 



