300 



OKGANOGRAPHT. 



guished by the varying attachment of the placentas and seeds 

 in the two cases ; thus in the former instance, each valve will 

 bear the placentas and seeds on its two margins {fig. 666), and 

 the valves are said to be jplacentiferous at their borders ; in the 



Fig. 666, 



Fig. 667. 



Fig. 668. Fig. 669. 



Fig. 666. Fruit of a Gentian dehiscing in a 



septicidal manner. Fig. 667. Fruit of 



Heart's-ease (Fiototnco/or), dehiscing in a 



loculicidal manner. Fig. 668. Fruit or 



siligua of the Wallflower, showing the 

 separation of two valves from a replum, 



Fig. 669. Fruit of Celandine (Chelido- 



nium majus), with the valves separating 

 from the placentas. 



latter, the placenta and seeds will be attached to the centre 

 of each valve (fig. 667), and the valves are then said to be 

 plactntiferous in their middle. It sometimes happens, as in 

 the fruit of the Chelidonium (fig. 669), and Wallflower {fig. 

 668), 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 {fig. 601). 



In compound fruits with a free central placentation, the same 

 forms of dehiscence occur as in those with parietal placentation, 

 but here it is difficult in many cases to speak positively as to 

 the nature of the dehiscence, from the absence of seeds or dis- 

 sepiments upon the valves. The means usually adopted in such 

 cases is to count the number of the valves and compare their 

 position with that of the divisions of the calyx. Thus as the 

 different whorls of the flower in a regular arrangement alter- 

 nate with each other, the component carpels or ovaries of the 

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

 If the fruit therefore separates into as many portions as there 

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

 placed alternate to them, they represent the component carpels 

 or ovaries, and the dehiscence is consequently analogous to the 

 septicidal form ; if, on the contrary, the valves are equal and 



