INTRODUCTION TO BOTANY. xi 
A flower is, 
barren, or sterile, when it produces no seed. 
fertile, when it does produce seed. 
69. The flowers of a plant or species are said collectively to be, 
unisexual, or diclinous, when the flowers are all either male or 
female. 
monecious, when the male and female flowers are distinct, but on 
the same plant. 
dicecious, when the male and female flowers are on distinct plants. 
polygamous, when male, female, and hermaphrodite flowers are 
variously mixed on the same plant. 
70. A head of flowers, or capitulwm, is heterogamous, when male, female, 
hermaphrodite, and neuter flowers, or any two of these, are included in 
it; homogamous, when all the flowers are of one kind and structure. A 
spike or head is androgynous, when male and female flowers are mixed in 
it. (See Composite, Aroidee, Cyperacee, etc.) 
71. As the scales of buds are leaves undeveloped or reduced in size, shape, 
and consistence, and bracts are leaves likewise reduced in size and occa- 
sionally 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. 
72. To understand the arrangement of the floral parts let us take a 
complete flower, in which all the parts are free from each other; definite in 
number, ¢.e. always the same in the same species; and symmetrical or 
isomerous, t.e€. when each whorl consists of the same number of parts. 
The flower of Flax (Linum), of Crassula, or of Oxalis, answers to this 
description: the two first consist of 4, the last-named of 5 whorls of 
altered leaves, placed immediately one within the other. 
73. The Calyx forms the outer whorl. Its parts are called sepals. 
74. The Corolla forms the next whorl. Its parts, called petals, usually 
alternate with the sepals, i.e. the centre of each petal is immediately over 
the interval between two sepals. 
75. The Stamens form one or two or more whorls within the petals. 
If two, those of the outer whorl (the outer stamens) usually alternate with 
the petals, and are consequently opposite to the sepals ; those of the inner 
whorl (the zxner stamens) alternate with the outer ones, and are conse- 
quently opposite the petals. If there is but one whorl of stamens, they 
most frequently alternate with the petals; sometimes (as in Rhamnee and 
Primulacee) they are opposite the petals and alternate with the sepals. 
76. The Pistil forms the innermost whorl. Its parts, called carpels, 
usually (when definite and isomerous) alternate with the inner row of 
stamens. 
77. In an axillary or lateral flower (58) the wpper parts of each whorl 
(sepals, petals, stamens, or pistil), are those that are next the main axis of 
the stem or branch; the dower those that are furthest from it; the inter- 
mediate are said to be Jateral. 
78. 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-, ete., poly-, 
ee 2-, 3-, 4., 5-, 6-, 7-, 8-, 9-, =, many-, 
prefixed to a termination indicating the whorl referred to. 
79. Thus, a Flower is, 
disepalous, trisepalous, etc., as there are 2, 3, etc., sepals. 
dipetalous, tripetalous, etc., as there are 2, 3, etc., petals. 
diandrous, triandrous, ete., as there are 2, 3, etc., stamens. 
digynous, trigynous, etc., as there are 2, 3, etc., separate carpels. 
