428 NATURAL HISTORY OF PLANTS. 



The fruit is dry, formed of from five to a dozen shells, horny or 

 bony, furnished dorsally with wings, tubercles or prickles of various 

 shape. These shells separate definitely from each other ;' and be- 

 neath their thick indehiscent wall is found one or- several oblique 

 descending seeds, with fleshy exalbuminous embryo. 



Tributes consists of herbs, often extended upon the ground, and 

 covered with hairs. The leaves are opposite or alternate by abor- 

 tion, compound-paripinnate, 2 accompanied by two lateral stipules. 

 The flowers 3 are solitary on a level with the insertion of the leaves, 

 to which they are lateral. 4 Some fifteen species 5 of this genus are 

 distinguished, natives of all the warm and temperate regions of the 

 world. 



Beside Tribulus are ranged also other herbaceous Zygoplij/lle<2 : 

 Sisi/udi/e, consisting of plants from the Cape, having uniovulate 

 ovary cells, a fruit with five shells, dehiscing by their internal edge, 

 and spartioid stems, bearing compound-pinnate leaves ; and Aitgea, 

 from the same country, composed of plants with the habit and 

 foliage of certain Ficoidecs, and whose flowers, with concave recep- 

 tacle, have stamens inserted on the edge of a membranous, cylin- 

 drical disk, surrounded by trifid laminae similar to their filaments 

 sometimes described as petals, and a capsular fruit with ten mono- 

 spermous cells. 6 



Guaiacum (fig. 514) consists of woody American plants, taking us 

 back to the floral organization of Zygophyllum. The floral receptacle 

 is rather elongated, in the form of a small truncate cone in the 

 species of Guaiacum proper. The androceum is diplostemonous ; 



1 It is principally because of the differences Sibth., Fl. Grate, t. 372. — Reiciib., Ic. Fl. 

 presented by the fruit that Kallstrcemia has Germ., v. t. 161. — Harv. & Sond., Fl. Cap., i. 

 been generally distinguished [Scop., Introd., 352. — OlTV., FL Trop. Afr., i. 283. — GejSEB., 

 937 ;— Endl., Gen., n. 6031; — Ehrenbergia Fl. Brit. W.-Ind., 134. — A. Geay, Man., ed. 

 Mart,, Nov. Gen. et Spec, ii. 72, i. 163 (nee 5, 110. — Chapm., Fl. S. Unit.-SL, 64. — 

 Spbeng.); — lleterozygis Bge., Vers. Alt. PjL, Benth., Fl. Austral., i. 287. — Geen. & Godr., 

 82, not.]. The shells, indefinite in number, are Fl. de Fr., i. 327. — Walp., Rep., i. 403 ; ii. 

 united into an angular pyramid on a common 242 {Trilulopsis), 822; iv. 403; Ann., i. 149; 

 axis extending beyond them above, and from ii. 2 12, 211 ( Kallstrcemia) ; v. 403; vii. 477, 

 which they afterwards separate without opening; 478 {Trilulopsis). 



within they present a groove, and without 6 Near these genera is placed Sericodes, a 



rugose unequal crests. ramose shrub of Mexico, unknown to us, having 



2 Or rather, douhtless, by the parts being simple sessile fasciculate leaves with small spi- 

 drawn up, one of the leaves remaining at a nescent stipules and fasciculate flowers, with 

 given level, while the other is more or less five persistent sepals, five entire petals, ten sub- 

 elevated beyond upon the axis of the plant. porigynous stamens, with five uniovulate ovary 



3 Yellow or white. cells, and a fruit whose five very velvety shells 



4 Consequently also caused by the drawing are indehiscent, and separate at maturity from 

 away of the parts. the columella. The ovules are descending. 



5 H. 13. K., Nov. Gen. et Spec, vi. 11.— 



