INTRODUCTION 



various-ly-shaped, sticky surface to which the grains of pollen 

 adhere when dropped on to it, fir carried thither by wind or 

 insects. Besides noting whether the 'ovary is apocarpous or 

 syncarpous, its external lorm, and the number of chambers into 

 which it may be divided infernally, it is important to determine 

 whether it is superior, free, that is, from the calyx, or inferior, 

 that is, adherent to the calyx- tube, and also how many ovules 

 there are in each chamber, and how 'they are arranged. This 

 arrangement is termed placentation, becSuse the ovules commonly 

 spring from a spongy cushiondike portion of the inner wall of the 

 ovary called 2. placenta. As the solitary ovule in the Polygonacea., 

 in the Walnut and in the Gymnospermbus ^ Yew appears to be a 

 direct prolongation of the branch or 

 axis, it is called terminal. That of the 

 Compositce, though rising from the base 

 of the ovary and, therefore, termed 

 basal, is lateral to the axis ; whilst in 

 the Priiniilacece and in the Caryophyl- 

 laeea severak^ ovules springing from a 

 central axis in-a one-chamljered ovary, 

 they are caW&d. free-central. In Water- 

 lilies, Poppie^i and the Flowering-rush 

 {Biitonius) the placentation is super- 

 ficial, the ovules beiig scattered over 

 the inner walls of the ovary. Most 

 one-chambered ovaries which contain 

 many ovules, such as that of the Violets, 

 have lines of ovules down their sides, 

 corresponding to the number of carpels. This is called parietal 

 placentation {La.im paries, a wall). The; Cruciferm are exceptional 

 in having parietal placentation in a two-chambered ovary, a 

 partition (known as a replum) growing across between the two 

 placentas (p. 31). Most many-chambsred ovaries have central 

 placetitatioii, as, for example, in the Lilies or St. John's worts, in 

 which the rows of ovules spring from the central axis formed by 

 the inrolled m.argins of the united carpels. 



The Fruit is the ovary and other adherent parts that enlarge 

 after the fertilisation of the ovules. Itimay be succulent or dry. 

 In the latter case, if one-seeded, it will generally be indehisceiit, 

 not splitting, that is, when ripe ; but . if many-seeded it will 

 commonly split, either into pieces know^^ as nutlets, each enclos- 

 ing one or two seeds, or so as to disclose its seeds. Our chief 

 types of fruit may be thus classified — 



1 NaJced-seeded. (.See p. x.\xii.) 



Diagram of apocarpous and .sy 

 carpous carpels with cross sectio 

 of their ovaries. 



