XXVI OUTLINES OF BOTANY. 



in number, i. e. always the same in the same species, and , 

 isomerous, i.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 upper 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-, 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) 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. 



And generally (if symmetrical), dimerous, trimerous, polymerous, etc., 

 according as there are 2, 3, or many (or an indefinite number of) parts to 

 each whorl. 



94. Flowers are unsymmetrical 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 th6 

 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 



