xxvi | OUTLINES OF BOTANY. 
in number, 7.e. always the same in the same species, and symmetrical or 
isomerous, t.e. when each whorl consists of the same number of parts. 
90. Such a complete symmetrical flower consists usually of either four 
or five whorls of altered leaves (88), placed immediately one within the 
other. 
The Calyx forms the outer whorl. Its parts are called sepals. 
The Corolla forms the next whorl. Its parts, called petals, usually 
alternate with the sepals; that is to say, the centre of each petal is imme- 
diately over or within the interval between two sepals. 
The Stamens form one or two whorls within the petals. If in two 
whorls, those of the outer one (the outer stamens) alternate with the petals, 
and are consequently opposite to, or over the centre of the sepals; those of 
the inner whorl (the inner stamens) alternate with the outer ones, and are 
therefore opposite to the petals. If there is only one whorl of stamens, 
they most frequently alternate with the petals; but sometimes they are 
opposite the petals and alternate with the sepals. 
The Pistil forms the inner whorl; its carpels usually alternate with the 
inner row of stamens. 
91. In an axillary or lateral flower the wpper parts of each whorl (sepals, 
petals, stamens, or carpels) are those which are next to the main axis of 
the stems or branch, the lower parts those which are furthest from it ; the 
intermediate ones are said to be lateral. The words anterior (front) and 
posterior (back) are often used for lower and upper respectively, but their 
meaning is sometimes reversed if the writer supposes himself in the centre 
of the flower instead of outside of it. 
92. The number of parts in each whorl of a flower is expressed adjec- 
tively. by the following numerals derived from the Greek :— 
mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octo-, ennea-, deca-, etc., poly- 
1-, 2-,  3-, 4., D-5 6-, 7T-, 8-, 9-, (ah many- 
prefixed to a termination indicating the whorl referred to. : 
93. Thus, a Flower is 
disepalous, trisepalous, tetrasepalous, polysepalous, etc., according as 
there are 2, 3, 4, or many (or an indefinite number of) sepals. 
dipetalous, tripetalous, polypetalous, etc., according as there are 2, 3, 
or many petals. 
diandrous, triandrous, polyandrous, etc., according as there are 2, 3, 
or many stamens. 
digynous, trigynous, polygynous, etc., according as there are 2, 3, or 
many carpels. XE 
And generally (if symmetrical), dimerous, trimerous, polymerous, etc., 
according as there are 2, 3, or many (or an indefinite number of) pazts to 
each whorl. 
94. Flowers are wasymmetrical or anisomerous, strictly speaking, when 
any one of the whorls has a different number of parts from any other; but 
when the pistils alone are reduced in number, the flower is still frequently 
called symmetrical or isomerous, if the calyx, corolla, and staminal whorls 
have all the same number of parts. 
95. Flowers are irregular when the parts of any one of the whorls are 
unequal in size, dissimilar in shape, or do not spread regularly round the 
axis at equal distances. It is, however, more especially irregularity of the 
corolla that is referred to in descriptions. A slight inequality in size or 
