DEHISCENCE 113 



is intensely adhesive, so that in falhng it does not readily bound away, 

 but becomes adherent to the first solid body which it encounters. 



Provisions for Scattering Seeds. — As a rule, fruits which are provided 

 with special de'S'ices for their transportation are not designed for the 

 discharge of the contained seed, which escapes accidentally or germin- 

 ates while still enclosed. Provisions for the discharge of seeds, therefore, 

 ordinarily apply only to such fruits as complete their function at the 

 place of origin. For provisions for the distribution of such plants, we 

 should naturally look to the seeds themselves; yet to this rule there are 

 numerous exceptions, for many fruits which never leave the place of 

 growth yet possess various devices for distributing their seeds over a 

 greater or less area by virtue of forces inherent in their pericarps. The 

 common name of the Impatiens, "touch-me-not," is derived from the 

 habit of its fruit of exploding with much force, discharging its seeds 

 meantime to a considerable distance. The fruit of Hura similarly 

 explodes, and ■with such violence as to cause a report like the discharge 

 of a firearm. Elaterium (Fig. 314), during the ripening process, collects 

 by osmosis within its cavity an amount of liquid which exerts a powerful 

 outward pressure upon the pericarp. When fully ripe, the slightest 

 contact with another body causes the pericarp to leap away from its 

 attachment, with the production of a hole at its base through which 

 the seeds are expelled with much force. 



Dehiscence. — The ordinary method of providing for seed discharge is 

 by means of a splitting of the pericarp known as Dehiscence. 



Dehiscent and Indehiscent Fruits. — A fruit so splitting is said to 

 Dehisce, and is known as a Dehiscent or Dehiscing fruit. Other fruits 

 are called Indehiscent. True dehiscence is longitudinal, although the 

 term is not altogether denied to other forms, provided the line of 

 separation is regular and constant (Figs. 325-327). 



The Valves. — The parts into which pericarps dehisce are called 

 Valves. The valves may separate entirely or remain attached in 

 various ways. 



Forms of Dehiscence. — Dehiscence may occur at the ventral or at the 

 dorsal suture or at both. If at the ventral, then the carpel (Fig. 349), 

 or each carpel if it be part of a polycarpellary pistil (Fig. 316), -will be 

 left entire. If the polycarpellary pistil have se^-eral cells, ventral 

 dehiscence must involve the separation of the carpels by the splitting of 

 their walls or septa, whereas in the one-celled form septa do not exist 

 or are incomplete. Nevertheless, the principle is identical in the two 

 cases, and the former mode is called Septicidal dehiscence (Fig. 316). 



