2474 



PARASITE 



PARKINSONIA 



ologists estimate that in the United States alone the 

 annual losses to crops from parasitic fungi and bacteria 

 amount to not less than $600,000,000. Parasitic fungi 

 commonly grow within the tissues of the host plant, 

 reaching the surface only when forming certain types 

 of spores, or propagative bodies. Parasites invariably 

 cause some disturbance of the normal development of 

 the tissues. Notwithstanding this fact, it can be said 

 that there are beneficial parasites, such as the bacteria 

 producing the nodules, or tubercles, on the roots of 

 legumes; and these nodules are important because of 

 the fixation therein of atmospheric nitrogen, which 

 ultimately becomes a source of nitrogen supply for the 

 legume host. 



There are also parasites among flowering plants. 

 Of these, two principal classes may be noted: (1) those 

 green in color, or chlorophyl-containing, such as the 

 mistletoe and the bastard toad-flax; and (2) those 

 practically devoid of chlorophyl, such as the dodder 

 and the broom-rape. The members of the first class 

 are commonly supposed to be active photosynthetically, 

 that is, they are able to manufacture their own car- 

 bonaceous food-supply from carbon dioxide and water, 

 while members of the second class must receive all or 

 nearly all similar foods through the host plant. Plants 

 living upon dead organic substance are termed sapro- 

 phytes (which see). There are all gradations between 

 parasites and saprophytes, especially among the fungi. 

 Some are parasitic during their more active vegetative 

 growth, and then continue their development saprophy- 

 tically. Again, there are many fungi which, while 

 generally parasitic, may be grown in the laboratory 

 upon a variety of culture media, or cooked plant prod- 

 ucts. Finally, there are those which ordinarily live 

 saprophytically in the soil, but under certain condi- 

 tions are able to induce disease epidemics. 



B. M. DUGGAB. 



PARATROPIA (Greek, turned away, probably with 

 reference to the twining habit). Araliaceae. Twining 

 trees or shrubs similar to Aralia, with compound Ivs.: 

 infl. paniculate or racemose. The genus is now included 

 in Schefflera by most authorities. P. Steltzneriana, 

 Barb.-Rodr. The plant intro. into Calif, under this 

 name grows up to 24 ft. high, evergreen: If. palmately 

 6-foliate; Ifts. leathery, oblong, short deltoid acumi- 

 nate, petioles articulate at the petiole. 



PARDANTHUS: Belamcanda. 



PARJETARIA (from parietarius, belonging to walls, 

 referring to its habitat). Urticacese. Annual or peren- 

 nial herbs widely scattered in the temperate zones, 

 scarce in the tropics. Fls. polygamous, cymose or 

 glomerate at the axils; perianth of the hermaphrodite 

 and male fls. deeply 4-lobed, rarely 3-lobed; lobes val- 

 vate; of the female fl. distinctly tubulous at the base, 

 lobes shorter; stamens 4, rarely 3; ovary free within the 

 perianth; stigma penicillate, short or linear: achene 

 included in the persistent perianth. Ten or more 

 species. P. arborea, Ait., an erect shrub, with Ivs. 

 perfectly white underneath, has been offered in trade- 

 lists. This belongs in the genus Gesnouinia, differing 

 from Parietaria in being small trees with the involucre 

 subtending 3-fld. glomerate -panicled branches: fls. 

 monoecious, the central pistillate, with the achene 

 included in the tube of the involucre. Gesnouinia con- 

 tains 2 species belonging to the Canary Isls. 



PARIS (the berry of the plant is compared to the 

 apple of discord, while the four leaves surrounding it 

 are likened to Paris and the three envious goddesses, 

 Juno, Minerva, and Venus. Others think the name is 

 derived from par, equal, referring to the agreement in 

 number between leaves and floral parts, and this is 

 probably the correct derivation). Liliacex. HERB-PARIS. 

 LOVE-APPLE. Hardy small herbs. 



Differs from Trillium in having its floral parts in 4's 

 instead of 3's. There are about 6 species altogether, 

 and in some of them the floral parts are in higher num- 

 bers than four. They resemble trilliums in being small 

 hardy rhizomatous plants, found in mountainous coun- 

 tries of the North Temperate Zone, and even in the 

 arctic regions; also they have a single whorl of lys. at 

 the top of the scape and a single fl., but in Paris the 

 outer perianth-segms. are more herbaceous and calyx- 

 like, while the inner ones are much narrower and less 

 showy, being mere strips of petal, or even entirely 

 absent. 



quadrifdlia, Linn. HERB-PARIS. TRUE-LOVE. FOUR- 

 LEAVED GRASS. Height 9-12 in. : Ivs. all cauline, netted- 

 veined (exceptional among monocotyledons) : peduncle 

 rising 1-2 in. above Ivs. : perianth-segms. yellowish green, 

 the 4 inner ones rather more yellow: berry bluish black. 

 The dominant European type, scattered over Eu. and 

 Siberia from the Arctic Circle to the Medit., in woods 

 and shady places, but usually local. Gn. 31, p. 165. 

 Fls. in spring or early summer. Rarely the Ivs. and floral 

 parts are in 5's. WILHELM MILLER. 



PARfTIUM : Hibiscus elatus and H. tiliaceus. 

 PARK: Landscape Gardening, page 1801. 



PARKIA (named after Mungo Park, born in 1771). 

 Leguminbsse. Tall unarmed trees: Ivs. evenly bipin- 

 nate; Ifts. very numerous, small: fls. in dense, long- 

 peduncled, obovoid heads; calyx tubular, shortly 

 5-cleft; corolla tubular, somewhat cleft; stamens 10; 

 ovary stalked: pod large, flat, strap-shaped, coriace- 

 ous. About 10 species, tropics of both hemispheres. 

 P. timoriana, Merr. CUPANG. A very large tree, up 

 to 115 ft. high, with vase-shaped, wide-spreading 

 crown: Ivs. fernlike, with very small Ifts.: fls. small, 

 white and yellow, in dense pear-shaped panicles: pods 

 pendulous, flattened, black, 18 in. long. Timor and 

 Philippines. Intro, in U. S. by Dept. of Agric. and 

 offered for distribution. 



PARKINSONIA (John Parkinson, 1567-1629, Lon- 

 don apothecary, author of the delightful "Paradisus 

 Terrestris" ana "Theatrum Botanicum"). Legumi- 

 nbsse. Tropical trees or shrubs, with a thin smooth 

 bark and armed with simple or three-forked spines. 



Leaves alternate or fascicled, bipinnate, with 1-4 

 pairs of pinnae; the common petiole short, often obsolete 

 or spinescent; stipules minute or none: fls. yellow or 

 whitish, on slender pedicels in short, loose axillary or 

 terminal racemes; calyx 5-parted, produced at base 

 and jointed upon the pedicel; petals 5, clawed, the 

 upper one within and broader than the rest, somewhat 

 cordate, the claw pubescent and nectariferous on the 

 inner side; stamens 10, free, the upper one gibbous 

 outside; ovary several-ovuled, shortly stipitate: pod 

 compressed, leathery, 2-valved, linear to linear-oblong, 

 more or less twisted, tapering at both ends; seeds 

 compressed, albuminous, with a crusty brown testa. 

 Five species. The dominant type, both in the wild and 

 in cult., is P. aculeata, the Jerusalem thorn, which is 

 probably a native of Amer., but is naturalized or cult, 

 in all tropical countries. One species is S. African, one 

 is S. American, and the remainder belong to the region 

 between Texas and S. Calif. P. aculeata is a thorny 

 evergreen tree with feathery drooping branches and 

 handsome yellow fls. ; it is admirable for hedges, thrives 

 in the driest places and can endure some cold. It has 

 been cult, in European conservatories, being usually 

 raised from imported seeds, but it is of difficult cult. 

 P. Torreyana, though generally destitute of Ivs., is 

 known in N. Mex. as "palo verde," from the bright 

 green color of the branches. It stands drought even 

 better than P. aculeata. These plants belong to the 

 same tribe with such fine northern trees as Gleditsia 



