276 



OEGANOGRAPHT 



the ovaries of the component carpels is placed in a similar posi- 

 tion to the simple ovary, and hence the placentas situated at 



their ventral sutures will 



Fig. 614. 



be arranged in the centre 

 or axis, as in the Lily 

 {fig. 615), and Campa- 

 nula {fig. 616). By 

 many botanists this mode 

 of placentation is called 

 central, and the term 

 axile is restricted to the 

 form of placentation 

 ■where the placenta is 

 supposed to be a prolon- 

 Fig. 614. Vertical section of the flower of oration of the axis. This 

 the Stonecrop. pi. Placenta of one of the ° •■^^ ■, n. j -, 



ovaries arising from the ventral suture. Will be atterwards al- 

 luded to. 

 In a compound one-celled ovary there are two forms of placen- 

 tation, namely, the parietal, and the free central. The placenta- 

 tion is termed parietal, when the ovules are attached to placentas 

 either placed directly on the inner wall of the ovary, as in the 

 Mignonette {fig. 607), and Cactus ( fig. 617), or upon incomplete 



Fig. 615 



Fig. 61 ( 



Fig. 617. 



Fig. 615. Transverse section of the compound ovary of the Lily. The 



ovary is trilocular. The placentas, pi, are axile. Fig. 610. Transverse 



section of the ovary of a species of Campanula. The ovary is flve- 



celled, and the placentation, vh axile. Fig. 617. Transverse section 



of the ovary of a species of Cactus. The ovary is unilocular, and the 

 placentation parietal. 



dissepiments formed (as already noticed) by the partially in- 

 folded ovaries, as in the species of Orchis {fig. 608) and Poppy 

 {fig. 609). In parietal placentation, the number of placentas 

 corresponds to the number of carpels of which the ovary is 

 formed. When the placentas are not attached to the wall of 

 the ovary, but are situated in the centre of the cavity and per- 

 fectly unconnected with the wall, they form what is called a 

 free central -placenta, as in the Caryophyllacese {figs. 619 and 

 620) and Primulacese {fig. 621). 



