XXX 



INTRODUCTION 



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

 adhere when dropped on to it, or 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 in ernally, it is important to determine 

 whether it is superior^ free, that is, from the calyx, or i?zferw?\ 

 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 p/acenfation, because the ovules commonly 

 spring from a spongy cushion-like portion of the inner wall of the 

 ovary called a placenta. As the solitary ovule in the Folygonacece^ 

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

 direct prolongation of the branch or 

 axis, it is called termmal. That of the 

 CompositcB^ though rising from the base 

 of the ovary and, therefore, termed 

 basal, is lateral to the axis ; whilst in 

 the Primulacece and in the Caryophyl- 

 lacecB several ovules springing from a 

 central axis in a one-chambered ovary, 

 they are cdiWed. free-ce?iij'al. In Water- 

 lilies, Poppies, and the Flowering-rush 

 i^Butomus) the placentation is super- 

 ficial, the ovules bei ^g 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 {h^iim paries, a wall). The Cruciferce. are exceptional 

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

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

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

 placentation, 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. It may be succulent or dry. 

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

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

 commonly split, either into pieces known 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 Naked-seeded. (See p. xxxii.) 



syii- 



Diagram of apocarpous and 

 carpous carpels with cross sections 

 of their ovaries. 



