4 DEHISCENCE. [BOOK i. 



their sides, as in Rosacese and Chrysobalanacese, Labiatse 

 and Boraginacese. 



When a fruit has arrived at maturity, its pericarp either 

 continues perfectly closed, when it is indehiscent, as in the 

 hazel nut ; or separates regularly round its axis, either wholly 

 or partially, into several pieces : the separation is called dehis- 

 cence, and such pieces valves ; and the axis from which the 

 valves separate, in those cases where there is a distinct axis, 

 is called the columella. 



When the dehiscence takes place through the dissepiments, 

 it is said to be septicidal ; when through the back of the cells, 

 it is called loculicidal; if along the inner edge of a simple 

 fruit it is called sutural; if the dissepiments are separated 

 from the valves, the dehiscence is named septifragal. 



In septicidal dehiscence the dissepiments divide into two 

 plates and form the sides of each valve, as in Rhododendron, 

 Menziesia, &c. Formerly botanists said that in this sort of 

 dehiscence the valves were alternate with the dissepiments, 

 or that the valves had their margins turned inwards. This 

 may be understood from fig. 169., which represents the 



fg. 169. 



relative position of parts in a transverse section of a fruit 

 with septicidal dehiscence ; v being the valves, d the dissepi- 

 ments, and a the axis. 



fig. 170. 



In loculicidal dehiscence the dissepiments form the middle 

 of each valve, as in the lilac, or in the diagram 170., 



