SECT. II 



PHANEROGAM I A 



485 



which are termed placentas (Fig. 431 p). In apocarpous gynaecea 

 the ovules are thus borne on the united margins of the carpels, each 

 margin bearing a row of ovules (Fig. 431 s). This is termed the 

 VENTRAL SUTURE, while the midrib of the carpel forms the DORSAL 

 SUTURE. In syncarpous ovaries the ovules are similarly borne on the 

 margins of the coherent carpels. The placentation is termed PARIETAL 

 when the placentas form projections from the inner surface of the 

 wall of the ovary (Fig. 432 D). If the margins of the carpels project 

 farther into the ovary, and divide its cavity into chambers or loculi, 

 the placentas are correspondingly altered in position, and the placenta- 

 tion becomes axile (Fig. 432 B). In contrast to such true septa, 

 formed of the marginal portions of the carpels, those that arise as 

 outgrowths of the surface or sutures of the carpels, as in the Cruciferae, 

 are called false septa. By the upgrowth of the floral axis in the 



Fig. 433. — Different forms of gynaecea. A, Of Aconitiim NapcUiis ; B, of Linum usitatissimum ; 

 C, of Nirotiami rustica ; D, style and stigma of AchilliM Millefolium ; /, ovary ; ij, style ; 

 n, stigma. (After Beru and Schmibt, magnified.) 



centre of the ovary what is known as free CENTRAL PLACENTATION 

 comes about. The projecting axis cannot be sharply distinguished 

 from the tissue of the carpels. The septa, which were originally 

 present, are arrested at an early stage of development or completely 

 disappear, so that the ovules are borne on the central axis covered 

 with carpellary tissue and enclosed in a wall formed by the outer 

 portions of the carpels. 



Each carpel is usually prolonged above into a stalk-like STYLE 

 terminating in a variously shaped stigma. The stigma serves as the 

 receptive apparatus for the pollen, and in relation to this is often 

 papillate or moist and sticky (Fig. 433 D). When the gynaeceum 

 is completely syncarpous, it has only one style and stigma. In 

 Fig. 433 an apocarpous {A) and a syncarpous gynaeceum (6') are 

 represented, together with one in which the carpels are coherent 

 below to form the ovary while the styles are free {B). 



The position of the ovules within the ovary may be erect, 



