158 VEGETABLE ORGANOGRAPHY. 



Capparideae, Fumariaceae, and some Papaveraceae, that 

 the margins of the carpels which do not extend into the 

 interior, or, if they do, by a very delicate lamina, are 

 however so united together that they cannot separate at 

 maturity. These united margins, together with the 

 placenta, form kinds of thick, firm nerves : the rupture 

 in this case takes place on each side along this nerve, 

 the whole of the intermediate part of the carpel is 

 detached and receives the name of Valve, and the 

 filament composed of the two placentae, united to the 

 margins of the carpels, is called the Intervalvular 

 placenta. An analogous phenomenon takes place in the 

 Orchideae. 



3d. It happens in some genera, with what are called 

 central placentae, that the carpels, after fecundation, 

 have a tendency to elongate beyond the placenta, the 

 partitions being, at the same time, very delicate and 

 easily broken, whilst the outer parts are strongly united 

 together both at the base and apex ; in these com- 

 plicated circumstances, the union of which is con- 

 sequently rare, the rupture takes place transversely 

 across the middle of the carpels: we call this Trans- 

 verse (circumscissa) dehiscence, of which Portulaca, 

 AnagalUs, &c. present examples. It is met with in the 

 Lecythideae with a peculiar combination. 



4th. Among genera with central placentae, the capsule 

 of which elongates after fecundation, and by this means 

 seems unilocular, at least at the upper part, it also fre- 

 quently happens that the outer portions of the carpels 

 remain united together the greater part of their length, 

 but at the upper extremity, they have a tendency either 

 to separate from one another or to split open along the 

 middle nerve ; this constitutes Apicilar dehiscence. 

 It is observed in a great number of the Caryophylleae : 

 the number of the teeth is equal to that of the carpels 



