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 immediately over or within the interval between two sepals.
Tlie Stamens form one or two whorls within the petals. If two, those of the outer whorl (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 wdiorl; its carpels usually alternate with the inner row of stamens.
91. In an axillaiy or lateral flower the npper 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 adjeetively by the following numerals derived from the Grreek: — mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octo-, eiinea-, deca-, etc., poly- 1-, 2-, 3-, -i-, 5-, 6-, 7-, 8-, 9-, 10-, 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) sepa-ls, 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, polygy^ious, etc., according as there 2, 3, or many carpels. And genei'ally (if s^^nmetrical), dimerous^ trimerous, polymerotcs, etc., according as they are 2, 3, or many (or an indefinite number of) parts to each whorl.
94. Flowers are tmsymmetrical or anisomerous, strictly speaking, when any one of the whorls has a difierent 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 whoi'ls 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 direction in the other whorls does not prevent the flower being classed as regular, if the corolla or perianth is conspicuous and regular.
§ 9. The Calyx and Corolla, or Perianth.
96. The Calsrx (90) is usually green, and smaller than the corolla; sometimes very minute, rudimentary, or wanting, sometimes very indistinctly whorled, or not whoi'led at all, or in two whorls, or composed of a large number of sepals, of which the outer ones pass gradually into bracts, and the inner ones into petals.
97. The Corolla (90) is usually coloured, and of a more delicate texture than the calyx, and, in popular language, is often more specially meant by the flower. Its petals are more rarely in two whorls, or indefinite in number, and the whorl more rarely broken than in the case of the calyx, at least when the plant is in a natural state. Douhle floivers are in most cases an accidental deformity or monster in which the ordinary munber of petals is multiphed by the conversion of 'stamens, sepals, or even carpels into petals, by the division of ordinary petals, or simply by the addition of superniunerary ones. Petals are also sometimes very small, rudimentary, or entirely deficient,
98. In very many cases, a so-called simple perianth (15) (of which the parts are