120 VEGETABLE ORGANOGRAPHY. 



the peduncles or flowers leave upon the stem or recep- 

 tacle. Sometimes they are found upon the organ which 

 is detached ; such are the Cicatrices which are observed 

 on the base of certain pericarps, as in the Acorn, — or 

 those on seeds, as in the Horse-chestnut. 



Dehiscence is a phenomenon which takes place in 

 organs which are closed, at least in their infancy; it is 

 nearly related to that which we call articulation in elon- 

 gated organs : it consists of a determined and regular 

 rupture, which is performed by a closed organ ; thus, 

 most dry fruits open when ripe, either longitudinally or 

 transversely, by one or several regular divisions. The 

 lines through which these ruptures take place, are most 

 frequently a little prominent, so that they can be per- 

 ceived before the dehiscence occurs : to these the name 

 of Sutures has been given, because they have been 

 compared to the projecting lines on pieces of cloth 

 which have been sewed together. But this term does not 

 indicate that the parts susceptible of separating by 

 dehiscence were always originally distinct ; in reference 

 to this there are two kinds of dehiscence. 



1st. It sometimes takes place between organs origi- 

 nally distinct, which have united during their growth, 

 and separate when ripe : this is what happens when the 

 carpels of a fruit separate from one another at their 

 points of junction,— as is seen, for example, m the Rho- 

 doraceaD or Colchicaceae ; when petals, which were more 

 or less completely joined together during flowering, 

 separate when they begin to wither, as in some species 

 of Correa. I give to this mode the name of Dehis- 

 cence by Separation (par decollement). The septicidai 

 dehiscence of fruits belongs to this class. 



2d. Sometimes parts originally distinct are united 

 together in such a manner that they cannot separate 

 when ripe, and then the dehiscence takes place by a 



