378 A TEXT-BOOK OF BOTANY. 



and the walls or partitions between the locules of a syncarpous 

 gynsecium are known as dissepiments; when three or more 

 carpels are united the number of dissepiments corresponds to the 

 number of carpels. It sometimes happens that a partition or wall 

 is intruded from the mid-vein of the carpel, dividing a unilocular 

 ovary into one that is bilocular, as in species of Astragalus, and 

 such a partition is termed a false dissepiment. 



When no other than the true dissepiments exist in the syn- 

 carpous gynaecium the placentas are borne along the axis of the 

 flower and are termed axial placentas. In the Caryophyllaceae 

 the ovules are borne upon a central axis, and the dissepiments 

 having been absorbed by the gynsecium is said txD possess a free 

 central placenta. In other cases the placentas grow backward 

 from the central axis toward the mid-vein of the carpel, carrying 

 the ovules with them, when they are spoken of as parietal pla- 

 centas, as in colocynth fruit and watermelon. 



The Style not only varies in shape and size but in the manner 

 of attachment to the ovary (Fig. 219) ; it may be very short, as in 

 the clove; long and filiform, as in (Enothera; club-shaped (clav- 

 ate), as in the orange; or broad and petalloid, as in Iris. It is 

 usually situated at the summit of the ovary, when it is said to be 

 apical or terminal; it may, however, be laterally attached, as in 

 the strawberry, or, as in a few instances, attached to the base of 

 the ovary. It is usually smooth, but may be hairy, as in the Com- 

 positae. The styles, like the carpels, may be separate or united, 

 and in the latter case may have a central canal connecting the 

 stigma with the ovary, as in the violets. While usually deciduous, 

 the style may be more or less persistent — forming a part of the 

 fruit — or even become much elongated, as in the dandelion. 



The Stigma is an essential part of the pistil in that it is the 

 germinating surface for the pollen grains, it being viscid and espe- 

 cially adapted for this purpose (Fig. 219). The stigmas may be 

 separate, as in the Compositae, or they may be united into a more 

 or less club-shaped or globular head, consisting of as many lobes 

 as there are stigmas^ as in the poppy. The stigma, while usually 

 solid, may have an opening, as in the violets, which sometimes has 

 a lid-like appendage, as in Viola tricolor. 



The Ovules (Fig. 219), as we have already seen, are small 



