ORGANS OF EEFEODUCTION, 295 



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, inclehiscent. Those fruits, such as the 

 Nut, Cherry, Apricot, Plum, and Date, which have very hard 

 or fleshy pericarps, are usually indehiscent. 



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

 down in the line of one or both of the sutures ; or at the junc- 

 tion of the component ovaries only, or at these 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 ovaries, or they are twice as numerous. 

 Thus in fruits formed of a single carpel or ovar}-, which only 

 open by the ventral or dorsal suture, there will be only one 

 valve corresponding to the one ovary, or its one cell ; but if the 

 carpels open by both sutures, there will be two valves. In 

 fruits formed of compound ovaries composed of several cells, the 

 valves will be equal in number to the cells, or component ovaries, 

 if the dehiscence only takes place by the dorsal suture or in the 

 line of union of the component ovaries ; or they will be double 

 the number, if the dehiscence takes place by both these parts 

 of the fruit. In compound one-celled fruits, the valves will be 

 equal in number to the component ovaries, if the dehiscence 

 occurs only by the ventral or dorsal sutures, or double, if by both 

 sutures. When there is a distinct axis left after the separation 

 of the valves, this is called the columella {figs. 661 and 662, a). 

 According to the number of valves, the fruit is described as 

 wii valvular, bivalvidar, trivalvular, multivalvular, &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- 

 lar, 2. Transverse or circumscissile, and 3. Porosis. 



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

 complete; thus, in Dianthus {fig. 650), Lychnis {fig. 649), 

 and many other Carj'ophyllaceous Plants, the dehiscence only 

 takes place at the upper part of the fruit, which then appears 

 toothed, the number of teeth corresponding to that of the valves. 

 A somewhat similar mode of partial dehiscence occurs in cer- 

 tain Saxifrages, and in the Mignonette {fig. 651), &c. ; in the 

 latter plant one large orifice may be observed at the summit 

 of the fruit at an early stage of its growth, and long before the 

 seeds are ripe. All these modes of partial dehiscence are by 

 some botanists placed under the head of porous dehiscence, but 

 from which, in most cases at least, they are really distinguish- 



