2650 



PISTACIA 



PITCAIRXIA 



copses along the coast of 15,000 hectares in extent. 

 It is the mastic tree of the island of Chios. The gum is 

 obtained by making transverse incisions in the bark. 

 This gum is in constant use by Turkish and Arab women 

 in the harems under the impression that it whitens the 

 teeth and perfumes the breath. Oil is pressed from the 

 seeds, one hundred kilos producing twenty litres of oil. 

 It is used by the Arabs for food and lights. The flexible 

 twigs are used by the same people for baskets. 



mexicana, HBK. A small shrub or tree: Ivs. odd- 



E innate on a somewhat winged or angled slightly 

 airy petiole; Ifts. 9-12 pairs, ovate or cuneate, obtuse, 

 glabrous, }/<$&. long, oblique at the base: fls. in axillary 

 panicled spikes fr. 1M~2 lines diam., smooth and some- 

 what compressed. Mex. and Calif. A very ornamental 

 shrub or small tree, sparingly in cult. 



m&tica, Fisch. & Mey. Tree up to 35 ft. high: the 

 bark dark brown with longitudinal fissures: Ivs. decidu- 

 ous, odd-pinnate; Ifts. 2-4 pairs, oblong or oblong- 

 ovate, obtuse; the petioles marginate or slightly winged, 

 puberulent: drupe 1J^ in. long, obovate, flattened, 

 obliquely apiculate. Asia Minor. The heartwood is 

 dark brown and very hard. Some cultivators dislike 

 it as a stock for P. vera, finding difficulty in making the 

 grafts take. 



vera, Linn. PISTACHIO. Small tree up to 30 ft. high, 

 with spreading branches : Ivs. pinnate, at first tomentose, 

 then glabrous, somewhat coriaceous, borne on angular 

 petioles; Ifts. 1-5 pairs, ovate, obtuse, nearly sessile 

 (in one variety in cult, in Calif, the Ivs. have only 

 3-5 Ifts.): drupe ovoid, oblong, pedicelled, reddish and 

 wrinkled. Medit. region and Orient. The kernel has a 

 rich, oily, agreeable flavor and in different varieties is 

 either pale green or creamy yellow. 



F. TRACY HUBBARD. 



PISTIA (probably from Greek, pistos, watery; refer- 

 ring to its aquatic nature). Aracex. WATER-LETTUCE. 

 TROPICAL DUCKWEED. A small tender, perennial float- 

 ing herb desirable for aquaria. 



Flowers unisexual; spadix without appendage, 

 adnate to the back of the spathe; male fls. in whorls, 

 with 2 very short stamens which are much grown 

 together and inserted at the apex of the spadix; female 

 fls. solitary; ovary 1-celled; ovules numerous, orthpt- 

 ropous, in 4-6 series: fr. baccate, irregularly breaking 

 open, normally with many seeds. Botanically, the 

 genus Pistia is unique. The monographer of the aroids 

 (Engler, in DC. Monogr. Phaner. 2, 1879) makes Pis- 

 tia the sole representative of a subfamily, one of his 

 10 primary natural divisions of the arum family. He 

 regards the pistias as all one species, though 9 or more 

 have been described. He recognizes 4 well-marked 

 varieties, based upon the shape of the Ivs., which he 

 calls cuneata, spathidata, obcordata and linguiformis. 

 After the continental fashion Engler takes no one of 

 these as a type to which the others are referred. It is 

 probable that the form with obcordate Ivs. is the one 

 chiefly cult, in American water-gardens. It forms a 

 loose rosette of Ivs. and has long slender feathery 

 roots. The plant sends out runners on which may some- 

 times be seen young plants in all stages of development. 

 A healthy plant measures about 6 in. across. The Ivs.' 

 are generally more or less wedge-shaped, 2-5 in. long, 

 pea-green, velvety to the touch, and covered beneath 

 with a sort of mealy down. The pistia rosette has been 

 compared to a half-grown lettuce plant before the head 

 has formed. Like many other aquatics, the water-let- 

 tuce has an immense range. It is found in fresh waters 

 throughout the tropics, and in the U. S. is native from 

 Fla. to Texas. 



Water-lettuce is commonly grown outdoors in sum- 

 mer in collections of tender aquatics, and also in 

 aquaria. The summer temperature of the water should 

 be 70 to 80 F. Although it grows well when floating free 

 in several feet of water, it seems to do better when 



placed in shallow water where the roots may reach the 

 soil. Larger-sized plants may be secured by using a 

 thin layer of rich soil or well-rotted manure in the 

 bottom of the vessel. Soft water is said to be essential. 

 Running water is not necessary. The plants should be 

 shaded during the middle of the day in summer, or the 

 foliage is likely to become yellow and sickly-looking. 



Stratidtes, Linn. WATER-LETTUCE. TROPICAL DUCK- 

 WEED. Tender perennial aquatic herb already described. 

 The small white fls., though inconspicuous and borne 

 at the bottom of the cup of Ivs., are large enough to 

 show at a glance their relation to the arum family. 

 B.M. 4564. F.S. 6:625. J.F. 2:137. Var. spathulata, 

 Engler. Lvs. spatulate, velvety green, more deeply 

 nerved than the type. S.E. U. S., Trop. Amer. 



WILHELM MILLER. 



PISUM (Greek and Latin name of pea). Legumi- 

 ndsse. Mostly tendril-climbing herbs of the Medit. 

 region and eastward, one of which is the common pea. 

 Hardy annuals or perennials of easy culture, growing 

 well in the cooler months: calyx-tube oblique at the 

 base, the lobes more or less leafy; standard obovate or 



orbicular; wings 

 adhering to the 

 keel; style mostly 

 rigid, widened 

 above, bearded 

 down the inner 

 margin: Ifts. 1-3 

 pairs, the If. end- 

 ing in a tendril or 

 point, the stipules 

 conspicuous. 

 Species about a 

 half dozen. 



sativum, Linn. 

 GARDEN PEA. Fig. 

 2987. Annual, 

 glabrous and 

 glaucous, tendril- 

 climbing: stipules 

 large and leafy 

 (usually as large 

 as Ifts.): Ifts. oval 

 or ovate, 2-3 pairs, 

 the If. ending in 

 tendrils; fls. few, 

 seeds globular. Eu., 



2987. Pisum sativum. ( X Ji) 



on an axillary peduncle, white 



Asia. The pea runs into many forms, which have been 

 variously named. Two major types of garden peas are 

 those grown for the seeds (shelling peas) and those 

 grown for the edible pods (sugar peas). See Pea. 



Var. arvense, Poir. (P. arvense, Linn.). FIELD PEA. 

 Fls. usually bluish, light lilac, or dull white, with purple 

 wings, and greenish keel, 1-3 on peduncle about as long 

 or little longer than stipules: seeds angular, often gray. 

 Grown for forage. 



Var. saccharatum, Hort. SUGAR PEA. Fls. mostly 

 in 2's: pod large and soft, more or less fleshy, sweet, not 

 dehiscing, edible. L. H. B. 



PITANGA : Eugenia uniflora. 



PITCAIRNIA (W. Pitcairn, a London physician). 

 Bromeliacex. Billbergia-like very short-stemmed per- 

 ennial herbs or subshrubs. 



Leaves in dense rosettes, narrow, often prickly-mar- 

 gined: infl. a central spike or raceme of long-tubular 

 red, yellow or nearly white fls.; fls. perfect; sepals 3, 

 free; petals 3, unguiculate, erect or spreading at the 

 apex, usually with 2 small scales at the base; stamens 

 6, free, with linear anthers: fr. a 3-valved caps., with 

 numerous seeds. Mez, the recent monographer of the 

 bromeliads (in DC. Monogr. Phaner. 9), admits 134 

 species of Pitcairnia. See also Baker in Journ. Bot. 



