XXIV INTRODUCTION. 



neuter ', when both stamens and pistil are imperfect or wanting. 



barren or sterile, when from any cause it produces no seed. 



fertile, when it does produce seed. In some works the terms barren, fer- 

 tile, and perfect are also used respectively as synonyms of male, female, and 

 hermaphrodite. 



86. The flowers of a plant or species are said collectively to be unisexual or 

 diclinous when the flowers are all either male or female. 



monoecious, wdien the male and female flowers are distinct, but on the 3ame 

 plant. 



dioecious, when the male and female flowers are on distinct plants. 



polygamous, when there are male, female, and hermaphrodite flowers on 

 the same or on distinct plants. 



87. A head of flowers is heterogamous when male, female, hermaphrodite, 

 and neuter flowers, or any two or three of them, are included in one head ; homo- 

 gamous, when all the flowers included in one head are alike in this respect. A 

 spike or head of flowers is androgynous when male and female flowers are mixed 

 in it. These terms are only used in the case of very few Natural Orders. 



88. As the scales of buds are leaves undeveloped or reduced in size and al- 

 tered in shape and consistence, and bracts are leaves likewise reduced in size, 

 and occasionally altered in colour ; so the parts of the flower are considered as 

 leaves still further altered in shape, colour, and arrangement round the axis, 

 and often more or less combined with each other.- The details of this theory 

 constitute the comparatively modern branch of botany called Vegetable Meta- 

 morphosis, or Homology, sometimes improperly termed Morphology (8). 



89. To understand the arrangement of the floral parts, let us take a complete 

 flower, in which moreover all the parts are free from each other, definite in 

 number, i. e. always the same in the same species, and symmetrical or 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, caSled 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. 



The Stamens form one or two wdiorls within the petals. If two, those of 

 the outer whorl (the outer stamens) alternate with the petals, and are conse- 

 quently 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 alter- 

 nate with the petals j 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 tipper parts of each whorl (sepals, 

 petals, stamens, or carpels) aie those which are next to the main axis of the 

 stems or branch, the loiver parts those which are furthest from it ; the inter- 

 mediate 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 adjectively by 

 the following numerals derived from the Greek : — 



mono-, 



di-, 



tri-, 



tetra-, 



penta-j 



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. 



