CLASS DIANDRIA. 
131 
normal law, caused by some accidental circumstance in the 
growth and development of the parts of the flower. The num- 
ber of stamens is frequently half that of the divisions of the 
corolla : the lilac has two stamens, and a/b-^^r-parted corolla. In 
a plant with three stamens, the number three or six usually 
prevails in the divisions of the calyx, corolla, capsule, &c. A 
knowledge of this fact will assist us in determining the class of 
a plant : for example, if we have a flower whose calyx has ^6 
or ten sepals, and the divisions of the corolla are the same, we 
may expect, if the flower is a perfect one, to find either ^z;^ or ten 
stamens ; or if the divisions of the flower be two^ there will gen- 
erally be two or foit^r stamens ; if three^ either three or six sta- 
mens ; if foiir^ either y<9z^^^ or eight stamens. The mxmhQY five^ 
as divisions of the calyx, corolla, and capsule, is generally uni- 
ted to five or ten stamens, and found in XhQ fifth or tenth class. 
a. Another native plant of this class is the Veronica (Fig. 129, c). Of the sev- 
enty species wliich this genus is said to contain, no more than six or eight are com- 
mon to North America. The Veronica and the Circtea Loth turn black when dried; 
although they do not add to the beauty of an herbarium, they are desirable in a 
collection of plants, as our country contains few specimens to illustrate the second 
class of the Linnsean system, 
h. Among the exotics of this order we find a singular plant, peculiar to the East 
Indies, the NycxANTHEs arbor tristis, or sorrowful tree ; its boughs droop during 
the day, but through the night they are erect, and appear fresh and flourishing. 
The Olive ( Olea) is common on the rocks of Palestine ; it may now, according to 
the accounts of travelers, be found upon the same spot which was called eleven 
centuries before the Christian era the Mount of Olives, or Mount Olivet. 
169. Order Digynia^ two pistils. — Contains the sweet-scent- 
ed spring-grass (Anthoxanthum odoratum\ which is found in 
blossom in May ; to this grass the pleasant smell of new-made 
hay is chiefly owing ; its odor is like that of clover. This plant 
is separated, by the artificial system, from the other grasses on 
account of its having but two stamens. 
a. The Catalpa, an elegant tree with flat, cordate or heart-shaped leaves, is m- 
digenous to the Southern United States ; its white flowers striped with purple 
grow in panicles similar to the Horse-chestnut. Only one species is found in North 
A merica. 
110. Order Trigynia., three pistils. — Contains the genus 
pirER, one species of which, the nigrum.^ is the common hlach- 
pepper. The cayennepepper belongs to the genus capsictjm, 
which is found in the eighth class. The flowers of the Piper 
genus have neither calyx nor corolla ; the fruit is borne on a 
spadix. The Piperacece family, or natural order, consists of but 
the one genus, Piper, which contains many species. The Piper 
cubeba contains a peculiar principle in its fruit which is known 
in medicine as cubeb-^&^^QY \ another species of this genus 
«. Veronica — b. Nj ctaiithes— Olive.— -169. Second order — Catalpa.— 170. Order Trigy nia— Pep* 
^ev — Firat order of the third class. 
