INDEHISCENT AND DEHISCENT FEUITS. 



303 



a'v\ 



Fig. 539. 



thus rendered distinctly visible. When the fruit consists of several 

 mature carpels, all meeting in the centre, and united 

 together, then the dorsal suture is also visible ex- 

 ternally ; but in cases where the placentation is 

 ' either parietal or free central, the edges of the sepa- 

 rate carpels, being near the surface, may present also 

 externally the marks of the ventral sutures. 



Where the sutures are formed, there are usually 

 two bundles of fibro-vascular tissue (fig. 539), one 

 on each edge. The edges of the sutures are often 

 so intimately united as not to give way when the 

 fruit is ripe. In this case it is called indehiscent 

 (in, used in the sense of not, and dehisco, I open), as in the Acorn and 

 Nut ; at other times the fruit opens between the two vascular bundles, 

 either at the ventral or dorsal suture, or at both, so as 

 to allow the seeds to escape, and then it is dehiscent 

 (dehisco, I open). By this dehiscence the pericarp becomes 

 divided into different pieces, which are denominated 

 valves, the fruit being univalvular, bivalimlar, or multi- 

 valvular, etc., according as there are one, two,- or many 

 valves. These valves separate either completely or par- 

 tially. In the latter case, the divisions may open in the 

 form of teeth at the apex of the fruit, the dehiscence 

 being apicilar, as in Caryophyllacese (fig. 540 ■;;), or as 

 partial slits of the ventral suture, when the carpels are 

 only free at the apex, as in Saxifrages. 

 Indehiscent Fettits are either dry, as the Nut, or fleshy, as the 

 Cherry and Apple. They may be formed of one or several carpels ; 

 and in the former case they usually contain only a single seed, which 

 may become so incorporated with the pericarp as to appear to be 

 naked. Such fruits are called pseudospermous (-^evS^g, false, and 

 (f-rsj^a, seed), or false-seeded, and are well seen in the grain of Wheat. 

 In such cases the presence of the style or stigma determines their true 

 nature. 



Dehiscent Fruits, when composed of single carpels, may open 

 by the ventral suture only, as in the follicles of Pseony, Hellebore (fig. 

 539), and Calthea; by the dorsal suture only, as in Magnolias and 

 some Proteacese ; or by both together, as in the legume' of the Pea 

 and Bean ; in which cases the dehiscence is called sutural. When 

 composed of several united carpels, the valves may separate through 



g. 640. 



Fig. 639. A single carpel of HeUetorus foetidus after dehiscence, sd, Dorsal suture. 

 St), Ventral suture. The carpel, when mature, opens on the ventral suture, and fonns iJie 

 truit denominated a foUiole. Fig. 640. Capsule or dry seed-vessel of Cerastium triviale 

 after dehiscence, c, Persistent calyx, p. Pericarp dividing at the apex, v, into ten teeth, 

 wliich indicate the summits of as many valves united helow. 



