GYN^CIUM 



63 



GYNiECIUM. 



The whole collection of carpels of a single flower constitutes 

 the gynaecium. 



APOCARPOUS GYN^piUM. 



The simplest type of carpel met with amongst Angiosperms 

 is that of the Pea or Bean (fig. 91). Its summit is formed by 

 the stigma, which is connected by the stalk-like style with the 

 pod-shaped ovary. The ovary forms a closed vessel with a 

 single cavity, in which are -a number of ovules. That precise 

 part of the ovary upon which the ovules are immediately in- 

 serted is described as the placenta; 

 in this case the placenta assumes the 

 form of a protruding line running 

 straight up the one side of the 

 ovary, and bearing a double row 

 of ovules. The carpel of the Pea 

 looks much like a small leaf, the 

 two halves of which have folded 

 along the mid-rib and joined at the 

 margins, the ovules being attached 

 to the incurved margins. And we 

 assume that the carpel is a leaf 

 which has thus become coherent 

 at its margins. Figs. 89, 90, 91, 

 show the successive stages by whfch 

 such a carpel could have been built 

 from a leaf with marginal ovules. A Gymnosperm — Cycas — has 

 an open carpel, very like that shown in figure 89. When their 

 ovaries have become fruits, the carpels of the Christmas Rose 

 and the Winter Aconite are half-opened, as shown in fig. 90. 

 In a simple closed carpel like that of the Pea, the line which 

 corresponds to the fused margins of the leaf is termed the 

 ventral suture (fig. 119 vs), whilst the line which corresponds to 

 the mid-rib is the dorsal suture (ds). 



Each carpel of the Buttercup (fig. 60) is essentially like that 

 of the Pea, excepting that it contains only one ovule (p), which 

 is attached to the floor of the ovary-chamber. 



The flower of the Pea contains only one carpel : that of the 

 Buttercup has many carpels ; but in both cases the gynaecium 



Figs, 89-91. — Single carpels. 



