260 



STRUCTURE AND VITAL PROCESSES OF PLANTS 



tlie edges of a carpellary leaf are joined is termed its veuti-al 

 suture. It is there that usually the ovules are attached alter- 

 nately, one right, the other left. The mid-rib of thr carpellary 

 leaf is its dorsal suture. Such is the structure of an ovary that 

 consists of a single carpel, as the Pea. Take any leaf, preferably 

 a lanceolate one, bend its edges over the mid-rib so that they 

 come together, and you produce something not unlike a pea pod. 

 If there are several free or apocarpous carpels, they are arranged 

 either radially or spirally on the receptacle (Vinca, Clematis, 

 Uvaria). In many cases, however, the carpels are connate and 

 form a syncarpoiis ovary, which contains one cavity or cell (also 



called locnlns). 

 Here the two 

 edges of each 

 carpellary leaf 

 do not join to- 

 geth er, but 

 touch those of 

 the neighbour- 

 ing carpels, 

 right and left, 

 as in the Orchis 

 or also in the Poppy. If the edges of each carpel do join one 

 another, they meet all in the centre of the ovary, which thus 

 becomes divided into two (Chilli), or three (Gloriosa), or as 

 many cells or loculi as the ovary is composed of carpels. The 

 ovules are usually attached to the edges of the carpellary leaves, 

 where a distinct growth, called the placenta, is formed. In a 

 many-celled ovary the placentation is axile, and in a one-celled 

 ovary that is composed of several carpels, it is usually parietal 

 (from Latin paries = yiii\\). In a few cases, however, the seeds 

 are not attached to the edges of the carpels, but to a pillar-like 

 growth in the centre of the ovary, thus forming a central placenta 

 (e,(j., in Antigonon, Basella). 



1. 2. 



Fig. 244. — Structure of ovary: 1- The ovary consists of one 

 carpellary leaf (Pea). 2. It is composed of 3 carpels 

 (Gloriosa). 3. Many carpels form the ovary (Poi)i)y). 



