ORGANS OF REPRODUCTION. 303 



similar disposition of the sutures- When an ovary, on the con- 

 trary, is formed of two or more carpellary leaves, the margins 

 of which are not inflected, or only partially so, and is therefore 

 one-celled, and presents parietal, or free central placentation, 

 both ventral and dorsal sutures may be observed externally al- 

 ternating with each other. The fruit, which is formed in a 

 similar manner, necessarily presents a similar alternation of the 

 sutures on its external surface. 



Dehiscence. — The pericarp at certain periods, which vary in 

 different plants, but commonly when the fruit is ripe, either 

 opens, so as to allow the seeds to escape, or it remains closed, 

 and the seeds can only become free by its decay. In the former 

 case, the fruit is said to be dehiscent ; in the latter, indehiscent. 

 Those fruits, such as the Nut, the Cherry, Apricot, Plum, Date, 

 &c., which have very hard or fleshy pericarps, are usually in- 

 dehiscent. 



Dehiscent fruits open in various ways: — 1st, By a sphtting 

 down in the line of one or both of the sutures ; or at the junction 

 of the component carpels only, or at those points, as well as 

 at the dorsal sutures ; in all such cases the pieces into which 

 the fruit separates are called valves, and these valves, when the 

 fruit is normal in its structure, are either equal in number 

 to the cells, or component carpels, or they are twice as nu- 

 merous. Thus in simple carpels, which only open by the vent- 

 ral or dorsal suture, there will be only one valve corresponding 

 to the one carpel, or its one cell ; but if they open by both su- 

 tures, there will be two valves. In compound ovaries composed 

 of several cells, the valves will be equal in number to the cells, 

 or component carpels, if the dehiscence only takes place by the 

 dorsal suture, or in the line of union of the component carpels ; 

 or they will be double the number, if the dehiscence takes 

 place by both those parts of the fruit. In compound one-celled 

 fruits, the valves will be equal in number to the component 

 carpels, if the dehiscence occurs only by the ventral or dorsal 

 sutures, or double, if by both. When there is a distinct axis left 

 after the separation of the valves, this is called the columella 

 {figs. 660 and 661, a). According to the number of valves, 

 the fruit is described as univalvular, bivalvular, trivalvularj mul- 

 tivalvular, &c. 



2nd, Dehiscence, instead of taking place longitudinally or in 

 a valvular manner, sometimes occurs in a transverse direction, 

 by which the upper part of the fruit separates from the lower 

 like the lid from a jar or box; and 3rd, It may take place in an 

 irregular manner by little pores. We have thus three kinds or 

 classes of dehiscence, which are called respectively: — 1. Valvu- 

 ar, 2. Transverse or circuinscissile, and 3. Porous. 



1. Valvular Dehiscence. — This may be either partial or 

 complete ; thus in the Dianthus {fig. 649), Lychnis {fig. 648), 



