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. 
Tribulus consists of herbs, often extended upon the ground, and 
covered with hairs. The leaves are opposite or alternate by abor- 
tion, compound-paripinnate,’ accompanied by two lateral stipules. 
The flowers are solitary on a level with the insertion of the leaves, 
to which they are lateral.‘ Some fifteen species’ of this genus are 
distinguished, natives of ail the warm and temperate regions of the 
world. 
Beside Zriéulus are ranged also other herbaceous Zygophyllee: 
Sisyndite, 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 Awgea, 
from the same country, composed of plants with the habit and 
foliage of certain Ficoidee, and whose flowers, with concave recep- 
tacle, have stamens inserted on the edge of a membranous, cylin- 
drical disk, surrounded by trifid laminæ similar to their filaments 
sometimes described as petals, and a capsular fruit with ten mono- 
spermous cells. 
Guaiacum (fig. 514) consists of woody American plants, taking us 
back to the floral organization of Zygophyllum. he 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 
presented by the fruit that Kallstremia, has 
Srptu., Fl. Grec. t. 372.—Retcus., Ic, Fl. 
Germ., v. t. 161,—Hary. & SoND., Fl. Cap., i. 
been generally distinguished [Scor., Jntrod., 
937 ;—Enpu., Gen., n. 6031 ;—Æhrenbergia 
Marzr., Nov. Gen. et Spec., ii. 72, i. 163 (nec 
SPRENG.);—Heterozygis BGE., Vérz. Alt. Pfl., 
82, not. |. The shells, indefinite in number, are 
united into an angular pyramid on a common 
axis extending beyond them above, and from 
which they afterwards separate without opening ; 
within they present a groove, and without 
rugose unequal crests. 
2 Or rather, doubtless, by the parts being 
drawn up, one of the leaves remaining at a 
given level, while the other is more or less 
elevated beyond upon the axis of the plant. 
3 Yellow or white. 
4 Consequently also caused by the drawing 
away of the parts. 
5 H, B. K., Nov. Gen. et Spec., vi. 11.— 
352.—Oniv., Fl. Trop. Afr., i. 283.—GRiSEB., 
Fl. Brit. W.-Ind., 184.—A,. Gray, Man., ed. 
5, 110.— CHarm., Fl. S. Unit,-St., 64.— 
Benta., Fl. Austral., i. 287.—GREN. & GopR., 
Fl. de Fr. i. 327.—Watp., Rep. i. 493; ii. 
242 (Tribulopsis), 822; iv. 403; Ann., i. 149; 
ii, 242, 244 (Kallstræmia) ; v. 403; vii. 477, 
478 (Tribulopsis). 
5 Near these genera is placed Sericodes, a 
ramose shrub of Mexico, unknown to us, having 
simple sessile fasciculate leaves with small spi- 
nescent stipules and fasciculate flowers, with 
five persistent sepals, five entire petals, ten sub- 
perigynous stamens, with five uniovulate ovary 
cells, and a fruit whose five very velvety shells 
are indehiscent, and separate at maturity from 
the columella, The ovules are descending. 
