PLACENTATION. 305 



the two constituent elements of the stigma (the only essential part 

 of the style) separate into two half-stigmas ; a tendency to which 

 is seen in Fig. 376, 377, and which is carried out in most spe- 

 cies of Drosera (Fig. 390). The stigma, no less than the placenta, 

 belongs to the margins of the infolded leaf (541), these margins 

 being ovuliferous in the ovary and stigmatiferous in the style ; as 

 Mr. Brown, the most profound botanist of this or any age, has 

 clearly shown. These two constituent portions of the style or 

 stigma are usually combined ; but are not unfrequently separate, 

 either entirely or in part, as in Euphorbiaceous plants, in Grasses, 

 and especially in Drosera, where there are consequently twice as 

 many nearly distinct styles as there are parietal placentae in the 

 compound ovary. If the two component parts of the style of each 

 carpel were reunited into one, in the usual manner, their number 

 would equal the placenta?, and their position would be alternate 

 with the latter. But since, in parietal placentation, each half-pla- 

 centa is confluent, not with its fellow of the same carpel, but with 

 the contiguous half-placenta of the adjacent carpel (555), it were 

 surely no greater anomaly for the elements of such half-stigmas 

 as those of Drosera (Fig. 390) to follow the same course. This 

 is precisely what takes place in Parnassia, and in other cases 

 where the stigmas are opposite the parietal placentae ; cases 

 which were thought to be very anomalous, merely on account of 

 the adoption of a false principle (that of the necessary alternation 

 of the stigmas and placentae), but which are really no more so 

 than the parietal placentation itself. The division of the style 

 in such cases furnishes further examples of collateral chorisis. 

 Sometimes the simple style is repeatedly forked in this way, or cut 

 into a fringe at the summit, as in Turnera, and the short lobes of 

 the compound style in Dionaea. 3. Furthermore, the production 

 of ovules is not always restricted to what answers to the margins 

 of the carpellary leaves. In the Poppy, the whole surface of the 

 long, imperfect partitions is covered with ovules ; in Butomus, they 

 are borne over the whole internal face of each carpel, and in the 

 Water-Lilies over the whole surface (Fig. 268), except the inner 

 angle of each cell, where alone they normally belong. Reduced 

 to two in the allied Water-Shield (Brasenia, Ord. Cabombaceae), 

 the ovules grow from the dorsal suture, or the midrib of the car- 

 pellary leaf alone ! And in Cabomba itself we usually find its 

 three ovules, one on the dorsal and one on the ventral suture, and 

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