MOEPHOLOGY OF THE FRUIT AND SEED 245 



instance, each valve bears the placentas and seeds oia its two 

 margins {fig. 522), and the valves are said to be placentiferous 

 at their borders ; in the latter, the placenta and seeds are 

 attached to the centre of each valve {fig. 515), and the valves 

 are then said to be placentiferous in their middle. It sometimes 

 happens, as in the fruit of the Wallflower {fig. 523), that the 

 placentas bearing the seeds remain undivided, and the valves 

 break away from them, so that they are left attached to a frame 

 or replum, which is a spurious dissepiment derived from the 

 placentas. 



In polyoarpellary fruits with a free central placentation, the 

 same forms of dehiscence occur as in those with parietal pla- 

 centation, but here it is difficult in many cases to speak 

 positively as to the nature of the dehiscence from the absence 

 of seeds or dissepiments upon the valves. The means usually 

 adopted in such cases is to count the number of the valves and 

 compare their position with the sepals or divisions of the calyx. 

 As the different whorls of the flower in a regular arrangement 

 alternate with one another, the component carpels of the 

 fniit should alternate with the sepals or divisions of the calyx. 

 If the fruit therefore separates into as many portions as there 

 are sepals or parts to the calyx, and if these valves are then 

 placed alternate to them, they represent the component carpels, 

 and the dehiscence is consequently of the septicidal form ; if, on 

 the contrary, the valves are equal and opposite to the sepals or 

 divisions of the calyx, each valve is composed of the adjoining 

 halves of two carpels, and the dehiscence is of the loculicidal 

 form. Sometimes the number of vah'es is double that of the 

 calycine segments or sepals, in which case each valve is formed 

 of half a carpel, the dehiscence of the fruit having taken place 

 both by its dorsal and ventral sutures. 



In all the above varieties of valvular dehiscence, the separa- 

 tion may either take place from above downwards, which is by 

 far the more usual form {figs. 513, 516, 519, and 521) ; or occa- 

 sionally from below upwards, as in the Celandine {fig. 524), 

 and universally in Cruciferous plants {fig. 523). 



In some fruits the carpels separate from each other without 

 opening, as in Scrophularia ; some of these show the axis 

 elongated, forming a columella or carpophore, as in the Mallow, 

 and in the Geraniaceie {fig. 526, a) and Umbelliferie {fig. 540). 

 The carpels which are united to it separate from it without their 

 ovaries opening. The ovaries of such carpels sometimes open 

 afterwards by their dorsal sutures {fig. 543, sd). When such 



