294 THE FLOWEK. 



and a single style. A pistil of two carpels may be two-celled, Avith 

 two placenta-!, two styles, or two stigmas, &c* 



* There arc, however, some exceptions which qualify these statements : — 

 1 Each placenta being a double organ (556) it occasionally happens that 

 the two portions arc separated more or less, as in Oiobanchaccous plants, where 

 a dicarpcllary ovary appears on this account to have four parietal placenta; ; 

 either approximate in pairs (as in our Cancer-root, Conopholis), or equidis- 

 tant (as in Aphyllon) 



2. Analogous to this is the case where the two constituent elements of the 

 stigma (the only essential part of the style) .separate into two half-stigmas, as is 

 partially seen in Fig. -194, 495. The stigma, no less than the placenta, belongs 



to the margins of the infolded leaf (545), these maigins being 

 ovnliforous in the ovary and stig matijerous 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 occasionally separate, cither entirely or in part, as in 

 Euphorbiaccous plants, in Grasses, and especially in Droscra 

 (Fig. 510), where there arc consequently twice as many neatly* 

 distinct styles as there arc paiietal placenta 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 placentas, and their position Mould be alter- 

 nate with the latter But since, in parietal placental ion, each 

 half-placenta is confluent (not with its fellow of the same 

 carpel, but) with the contiguous half-placenta of the adjacent cai pel, it wcic suiely 

 no greater anomaly for the elements of such hdlfsiiijmas as those of Droscra to 

 follow the same course. This is precisely what takes place in Farnassia, and in 

 other cases where the stigmas aic opposite the parietal placenta; ; — cases which 

 were thought to be very anomalous, merely on account of the adoption of a 

 false principle (that of the ncccssaiy alternation of the stigmas and placenta;), 

 but which arc really no more extraordinary than parietal placcntation itself 



3. Fmthcrmorc, the production of ovules is not always restricted to what 

 answers to the margins of the carpcllary leaves. In the Poppy, the whole sur- 

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

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

 the whole surface, except the inner angle of each cell, where alone they normally 

 belong. Reduced to two in the allied Water Shield (Brascnia, Fig. 684), the 

 ovules grow from the dorsal suture, or the midiib of the carpcllary leaf alone ! 

 And in the allied Cabomba itself we usually find its three ovules, one on the 

 dorsal and one on the ventral suture, and the third on some variable pail of the 

 face of the cell in the vicinity of cither suture. In Obolaria, Bartonia (Ccntau- 

 rclla, Michx ), and in several species of Gentian, a compound one-celled ovary is 

 ovuiiferous over the whole face of the cell ! 



All placcntation is very differently explained by those who adopt the hypoth- 



FIG. 610 Pistil of Drosera filiformis, with three deeply two-parted styles : the oyarj cut 

 tcrois, showing three parietal placentae. 



