Trihulus. ZYGOPHYLLACE^. 353 



* Herbs, with no albumen to the seed, an almoud-like embryo, and abruptly pinnate mostly 

 opposite leaves. 



1. TRIBULUS. Sepals and petals 5, rarely 4 or 6. Filaments slender, naked; those be- 

 fore the petals sometimes aduate to their bases ; the alternate ones with ahypogynous gland 

 behind each. Ovary sessile ; cells as many or twice as many as petals, 1-5-ovuled. Fruit 

 lobed, 5-10(-I2)-coccous, i. e. splitting at maturity into as many hard and closed nutlets, 

 these usually muricate or spinescent on the back. 



* * Herbs with albumen to the seeds and alternate leaves. 



2. PEGANUM. Sepals 4 or 5, foliaceous, often cleft or piunatifid, open in the bud, persist- 

 ent. Petals 4 or 5, lightly convolute in the bud. Stamens 12 to 15, inserted around a 

 low annular disk, one series alternate with the petals, the others in pairs before them ; fila- 

 ments naked ; anthers linear. Ovary 2-4-lobed, 2-4-celled ; numerous ovules in each cell 

 upon a central placenta; style slender, at length twisted, above acutely 2-4-angled and 

 the angles stigmatose. Capsule globose, coriaceous, tardily or imperfectly dehiscent, 

 many-seeded; seeds with spongy scrobiculate testa, and a slightly curved embryo in fleshy 

 albumen. 



* * * Woody or suffrutescent plants, with albumen to the seeds and opposite leaves. 

 •h- Leaves 1-3-foliolate : subherbaceous or suffruticose. 



3. FAGONIA. Sepals 5, deciduous. Petals .5, unguiculate, early deciduous. Stamens 10, 

 with filiform naked filaments and short anthers. Ovary sessile, 5-celled ; a pair of collateral 

 ovules in each cell. Fruit ovate, 5-lobed, subulate with the style, smooth, 5-coccous ; the 

 carpels separating from each other and from the styliferous axis, dehiscent ventrally, and 

 thin epicarp separable from the cartilaginous endocarp ; seed solitary, with mucilaginous 

 coat and horny albumen. 



-t— -(— Leaves abruptly pinnate ; leaflets from one to several pairs : calyx deciduous. 



4. LARREA. Sepals and petals 5. Stamens 10; filaments slender, bearing on the inside 

 near the base a conspicuous 2-cleft or laciniate petaloid scale ; anthers oblong. Ovary short- 

 stipitate, globular, 5-celled, about 3 pairs of ovules in each cell; style filiform; stigmas 5, 

 minute. Fruit villous, 5-lobed, 5-coccous ; the carpels 1-seeded, at maturity separating from 

 each other and from the slender axis, indehiscent ; embryo slightly arcuate in the horny 

 albumen ; its oblong cotyledons anterior and posterior in the carpel. 



5 GUAIACUM. Sepals and petals 5 or sometimes 4. Filaments naked or bearing a small 

 scale ; anthers oblong, incurved in age. Ovary variously stipitate, 2-5-angled, 2-5-celled, 

 and with 4 or 5 ])airs of ovules in each cell ; style slender-subulate ; stigma small. Fruit 

 glabrous, 2-5-coccous, coriaceous or at first fleshy; the carpels 1- or sometimes 2-seeded, 

 separating at maturity, ventrally and sometimes dorsally dehiscent ; seed with thick coat 

 and straight or somewhat curved embryo in horny albumen ; oval cotyledons with edges or 

 sometimes their faces ventral and dorsal in the carpel. 



1. TRIBULiUS, Toiirn. Caltrops. (Tpt'/^oXo?, ancient name of Trapa, 

 transferred by the herbalists to this genus.) — Prostrate or ascending herbs, 

 mostly pubescent, with abruptly pinnate leaves, some or in certain species all of 

 them becoming alternate by suppression of one of the pair, and yellow flowers on 

 simple peduncles. — Inst. 265, t. 141 ; L. Gen. no. 360; Benth. & Hook. Gen. 

 i. 264. Trihulus & KaUsfrcemia (Scop.), Endl. Gen. no. 6030, 6031 ; Gray, 

 Gen. 111. ii. 115, 117. t. 145, 146. 



§ 1. Calyx deciduous : cells of the ovary only as many as the petals, i. e. 5, 

 rarely 4, few-ovulate, forming as many nut-like spinescent or tuberculate 2-5- 

 seeded cocci which at separation leave no central axis ; the seeds superposed, 

 nearly horizontal and separated by transverse septa. — Trihulus, Scop. Introd. 

 253, &c. 



23 



