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TRIDACTYLIA, in Ornithology, a genus of birds, 

 feparated by Dr. Shaw from Picus, on account of the 

 number of toes ; this having but three, whereas the genuine 

 Pice are all furniihed with four. Its generic charafters are ; 

 beak many-fided, ftraight, wedge-ftiaped at the tip ; nof- 

 trils covered with fetaceous recumbent feathers ; and feet 

 with only three toes, placed two before and one behind. 

 The fpecies ai-e the following. 



HiRsuTA. Downy, varied with black and white. See 

 Picus TridaBylus. 



Undulata. Waved, varied with black and white, be- 

 neath white. The fouthern three-toed woodpecker of 

 Latham. Firft. defcribed by Briflbn, and by him faid to in- 

 habit Cayenne. 



TRIDAX, in Botany, from tfnq, three, and 5ax™, to 

 lite, or "uiound, becaufe of the three deep divifions of its 

 marginal florets. Such is the explanation of De Theis, and 

 it feems confonant with the meaning of Linnasus ; yet the 

 latter in his Philofophta Botamca enumerates this word, which 

 he confiders as fynonimous with SpiJji^, lettuce, among the 

 old Greek names incapable of explanation. Poffibly he 

 had forgotten his original idea, between the writing of his 

 Hortus CTiffort'tanus and the Philofophla ; efpecially as he 

 had not fince feen the plant. Pliny fpeaks of OJirea tridacna, 

 a kind of oy Iters, fo called becaufe one of them was large 

 ■enojgh for three bites, or mouthfuls. — Linn. Gen. 435. 

 Schreb. 568. Willd. Sp. PI. V. 2214. Mart. MiU. Dift. 

 V. 4. Juif. 190. Gaertn. v. 2. 451, no figure. — Clafs and 

 order, Syngenejia Polygamia-fuperjlua. Nat. Ord. Compo- 

 Jit£ oppofilifol'm, Linn. Corymbifcrie, Juff. 



Gen. Ch. Common Calyx cylindrical, imbricated, with 

 ovate-oblong, (harpi(h, upright fcales. Cor. compound, 

 radiant. Florets of the diik all perfeft, tubular, funnel- 

 fhaped, ereft, five-toothed ; thofe of the radius female, ligu- 

 late, in three deep fegments of equal length, the middle one 

 narrowed. Stam. in the perfeft florets. Filaments five, 

 capillary, very fliort ; anthers united into a cylindrical tube. 

 Pyi. in the perfedl florets, Germen oblong ; ftyle briftle- 

 ftiaped, the length of the ftamens ; fl;igma obtufe ; in the 

 female ones, Germen oblong ; ftyle thread-fliaped, the 

 length of the corolla ; ftigma obtufe. Peric. none, except 

 the permanent calyx. Seeds, in both kinds of florets, foli- 

 tary, oblong. Down fimple, rather longer than the calyx. 

 Recept. flat, clothed with lanceolate chaffy fcales, (horter 

 than the feeds. 



Efl". Ch. Receptacle chaffy. Down of many fimple 

 hairs. Calyx imbricated, cylindrical. Florets of the radius 

 in three deep fegments. 



I. T. procumbens. Procumbent Tridax. Linn. Sp. PI. 

 1268. Willd. n. I. Mill. Dea. ed. 8. (Tridax ; Linn. 

 Hort. Cliff". 418. After americanus procumbens, foUis la- 

 ciniatis et hirfutis ; Houftoun's MSS.) — Gathered at Vera 

 Cruz by Dr. Houftoun, who fent feeds to Miller. The 

 latter cultivated this plant, in his bark-ftove at Chelfea, but 

 it flowered fparingly, and feldom perfefted feed. He fent 

 a dried fpecimen to Cliffbrt, which Linnseus defcribed, but 

 there is none preferved in the Linnasan coUeftion, nor has 

 any figure of the Tridax ever appeared. It feems to be 

 herbaceous and perennial, propagating itfelf by the trailing 

 Jlems, which throw out roots, and are hairy, clothed with op- 

 pofite, nearly feffile, rough, hairy, ovate leaves, an inch 

 and half long, acute at each end, fliarply ferrated, their 

 loweft and largeft ferratures, which are about the middle of 

 the leaf, making a fort of angle at each fide. Floiuer- 

 Jlalks long, naked, fimple, at firft terminal, but afterwards 

 becoming lateral. Flowers folitary, creft, palifli copper- 



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coloured, or whitilh ; Linnscus erroneoufly fuppofed the 

 radius to be yellow. 



TRIDE, in the Manege, fignifies fliort and fwift : thus 

 a trtde pace, is a going of fliort and quick motions, though 

 united and eafy. A tride career is a very faft gallop, with 

 the times or motion fliort and nimble ; and fo of other mo- 

 tions. Some apply the word only to the motion of the 

 haunches. 



TRIDENT, Tridens, an attribute of Neptune; be- 

 mg a kind of fceptre, which the painters and poets put into 

 the hands of that god. It is in form of a fpear, or fork 

 with three prongs, whence the word. 



The poets tell us, that Neptune makes the earth open 

 whenever he ftrikes it with his trident. 



Mythologifts give feveral reafons for afligning to Neptune 

 the trident. Some fay that it was defigned to denote by its 

 three points, the quality of the three forts of waters that 

 are upon the earth ; thofe of the fea, which are fait ; thofe of 

 the fountains, that are fweet ; and thofe of the ponds, tliat 

 partake of both thefe qualities. Others fay, that it alludes 

 to Neptune's threefold power over the fea, which he trou- 

 bles, afluages, and preferves. But without hunting after 

 myfteries, it is fufiicient to allow, that the trident was a kind 

 of fceptre ufed by ancient kings. 



Trident, among Mathematicians, is ufed for a kind of 

 parabola, by which Defcartes conftrufted equations of fix 

 dimenfions. 



TRIDESMIS, in Botany, fo called by Loureiro, frona 

 TfEh", three, and lia-fjn:, a little tuft or bundle, defcriptive of 



the ftyles Loureir. Cochinch. 576. — Clafs and order, 



Monoecia Polyandria. Nat. Ord. Tricocct, LIbh. Euphor- 

 bia, .Tufl". 



Gen. Ch. Male, Col. Perianth of five lanceolate, hairy, 

 fpreading leaves. Cor. Petals five, lanceolate, downy, 

 nearly equal to the calyx, inferted into the receptacle. 

 Stam. Filaments about twenty, fliorter than the corolla ; 

 anthers oblong, creft. 



Female, at the bafe of the fame fpike, Cal. Perianth in- 

 ferior, of the ftrufture of the male. Cor. none. Pijl. 

 Germen fuperior, roundifli ; ftyles from fifteen to twenty, 

 thread-fliaped, longer than the ftamens, coUedled into three 

 bundles ; ftigmasthickifli. Peric. Capfule roundifli, briftly, 

 of three cells and three valves. Seeds folitary, angular at the 

 inner fide, gibbous externally. 



Eflf. Ch. Male, Calyx of five leaves. Petals five. Sta- 

 mens about twenty. 



Female, Calyx of five leaves. Corolla none. Styles nu- 

 merous, in three bundles. Capfule of three cells, with foli- 

 tary feeds. 



1 . T. hifpida. Briftly Tridefmis. Ki quat yong of the 

 Chinefe. Loureir. n. I. — " Leaves hifpid on both fides, 

 Spike fliort." — Found in bufliy places about Canton, in 

 China. An unbrancbed upright yZirui, about ten inches 

 high, with a perfeftly fimple, very long, vertical, twifted, 

 thick-barked root. Leaves fcattered, ovate, rather acute, 

 flightly ferrated. Floivers hi a fliort, fimple, terminal fpike. 

 A decoftion of the root is thought by the Chinefe to ftreng- 

 then the tendons and bones. 



2. T.tomentofa. Downy Tridefmis. Ca xi ma of the 

 Chinefe. Loureir. n. 2. — " Leaves downy beneath. Spike 

 elongated." — Found wild about Canton. Stem flirubby, 

 ereft, four feet high, with numerous afcending branches. 

 Leaves alternate, lanceolate, fomewhat ferrated. Flowers in 

 long, fimple, terminal fpikes. Stamens but ten. Stylet 

 fix, long, in three pairs. Capfule hairy. 



We cannot precifely reduce thefe plants to any known 



genus, 



