PLANT ORGANS AND ORGANISMS 



203 



layer. When the mesocarp is fleshy, as in the Peach, it is called the 

 sarcocarp. 



When the endocarp within the sarcocarp is hard, forming a shell or 

 stone, this is termed a putamen. 



Sutures. The ventral suture is a line formed by the coherent 

 edges of a carpellary leaf. The dorsal suture is the mid-rib of the 

 carpel. Parietal sutures are lines or furrows frequently visible on the 

 walls of fruits, formed by the ripening of a compound ovary. They 

 occur between its dorsal sutures and indicate the places of union 

 between adjacent septa or of two parietal placentae. 



Valves. These are the parts into which the mature fruit separates 

 to permit the escape of the seeds. Depending upon the number of 

 these the fruit is said to be univalved, bivalved, trivahed, etc. 



ABC 



FIG. 98. Diagrams illustrating three forms of valvular dehiscence. A, Locu- 

 licidal dehiscence showing each carpel split along its midrib or dorsal suture, 

 the dissepiments remaining intact; B, septicidal dehiscence, in which splitting 

 took place along -the partitions; C, septifragal dehiscence, in which the valves 

 broke away from the partitions. 



Dehiscence. This is the opening of the pericarp to allow the 

 seeds to escape. 



Fruits are either Dehiscent or Indehiscent according as they open to 

 discharge their seeds spontaneously when ripe (dehiscent), or decay, 

 thus freeing the seeds, or retain their seeds, the embryo piercing 

 the pericarp in germination (indehiscent) . Dehiscent fruits open reg- 

 ularly, or normally, when the pericarp splits vertically through the 

 whole or a part of its length, along sutures or lines of coalescence of 

 contiguous carpels. Legumes usually dehisce by both sutures. 

 Irregular or abnormal dehiscence has no reference to normal sutures, 

 as where it is transverse or circumscissile, extending around the cap- 



