50 



ESSENTIALS OF VEGETABLE PHAR\[ACOGNOSY 



The fixation of many fruits with their of the pericarp knowa as Dehiscence.' A 



fruit so splitting is said to Dehisce and 



contained seeds is secured by a series of 

 devices no less interesting than those 

 which affect their distribution. Fruits like 

 those represented in Figs. 61, 62 &c., 

 are commonly more or less sharpened or 

 narrowed at the lower end, w^hich is much 

 the heavier, so that they shall the more 

 readily penetrate a favorable surface. 



Their bodies, 



arc 



moreover, 

 toothed or hispid upward, so 

 tendency is for them to sink more 

 more deeply until properly interred, 

 fruit of Viscum, whose 



commonly 

 that the 



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. 279-282). 

 The parts into w^hich pericarps dehisce 

 are called Valves. The valves may sep- 

 arate entirely or remain attached in vari- 

 ous ways. Dehiscence may occur at the 



The ventral or at the dorsal suture or at both. 



Fry ZJJ. 



f -g lit 



Ti^m 



F,g.an., 



F.g.2T«. 



f.g.ast 



Fig. ai 9 . 



fig.lBOr 



8 



a8a. 



F.g.iea* 



seed can de- If at the ventral, then the carpel (Fig. 

 velop only upon the bark of trees, is in- 300), or each carpel if it be part of a 

 tensely adhesive, so that upon falling it polycarpellary pistil (Fig. 271), will be 

 can never bound away, but becomes ad- 

 herent to the first solid body which it 

 encounters. 



- As a rule, fruits which are provided 

 with special devices for their transporta- 

 tion are not designed for the discharge of 

 the contained seed, which escapes acci- 

 dentally or develops 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 nat- 

 urally look to the seeds themselves; yet 

 to this rule there are numerous excep- 

 tions, for many fruits which never leave left entire. If, as sometimes, the polycar- 

 the place of growth yet possess various pellary pistil have several cells, ventral 

 devices for distributing their seeds over dehiscence must involve the separation 

 a greater or less area by virtue of forces of the carpels by the splitting of their 

 inherent m their pericarps. The common 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 this form is called 

 Septicidal Dehiscence (Fig. 271). In the 

 former of these two cases the carpels, 

 after separating through their septa, are 

 not necessarily open, and unless the de- 

 hiscence shall follow the wall into and 

 through the ventral suture, which it rarely 

 does, the dehiscence will be Imperfect 

 and the carpels will act as separate in- 

 dehiscent fruits. If dehiscence occur at 

 the dorsal suture (Figs. 272 and so on) it 

 must separate the wall of the cell into 

 two parts, and this form is called Loculi- 

 cidal Dehiscence. By an intermediate 

 form the dehiscence takes place at the 

 point where the septum joins the outer 

 seed discharge is by means of a splitting wall (Fig. 273), the Marginicidal. Vari- 



S 



name of the Impatiens, "touch-me-not," 

 is derived from the habit of its fruit of 

 exploding with considerable force, dis- 

 charging its seeds meantime to a consid- 

 erable distance. The fruit of Hura simi- 

 larly explodes, but with such violence as 

 to cause a report like the discharge of a 

 firearm. Elaterium (Fig, 270), durin 

 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 at- 

 tachment, with the production of a hole 

 at its base through which the seeds an» 

 expelled with much force. 

 The ordinary method of providing for 



