INTRODUCTION. XV 



The Corolla forms the next wliorl. 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. Tlie 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 tlie parts of any one of tlie 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 descrip- 

 tions. 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 ordi- 

 nary 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 superniune- 

 rary 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 



c 2 



