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 bo, 

 tuiisexaal, or diclinous, when the flowers are all either male or 



female. 

 monoecious, when the male and female flowers are distinct, hut on 



the same plant. 

 dioecious, 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 capitulum, 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, Aroidece, Cyperacece, etc.) 



71. As the scales of huds 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 axe free from each other; definite in 

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

 isomerous, ^. 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 wdthin 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 inner 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 RhamnccB and 

 Frimulacece) 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 upper paris of each whorl 

 (sepals, petals, stamens, or pistil), are those that are next the main axis of 

 the stem or branch ; the lower those that are furthest from it ; the inter- 

 mediate are said to be lateral. 



78. The number of parts in each whorl of a flower is expressed adjec- 

 tively by the following numerals, derived fi'om the Greek : 



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, etc., as there are 2, 3, etc., stamens. 

 digynous, triyynous, etc., as there are 2, 3, etc., separate carpels. 



