ORGANS OF EEPEODUCTIOX. 



301 



Fig. 670. 



opposite to the divisions of the calyx, each valve is composed of 

 the adjoining halves of two ovaries or carpels, and the dehis- 

 cence is analogous to the loculicidal form. Sometimes the 

 number of valves is double that of the calycine segments, or 

 sepals, in which case each valve is formed of half an ovary or 

 carpel, the dehiscence of the fruit having taken place both by its 

 dorsal and ventral sutures. 



In all the above forms of valvular dehiscence, the separation 

 may either take place from above downwards, which is by far 

 the more usual form {figs. 655, 658, and 663); or occasionally 

 from below upwards, as in the Mahogany (Swietenia Mahagoni), 

 Chelidonium {fig. 669), and Cruciferous Plants (fig. 668). 



2. Transverse or Circumscissile Dehiscence. — In this kind 

 of dehiscence, the opening takes place by a transverse line 

 through the fruit across the sutures, so that the upper part is 

 separated from the lower like the lid of a 

 jar or box, as in Hyoscyamus {fig. 670), Ana- 

 gallis {fig. 693), and Purslane. Sometimes 

 the dehiscence only takes place half round the 

 fruit, as in Jeffersonia, in which case the lid 

 remains attached to the pericarp on one side, 

 as by a hinge. The transverse dehiscence of 

 fruits resembles that of certain forms of calyx, as 

 that of Euccdyptus a,nd Eschscholf^m, where the 

 upper part separates from the lower like a lid. 

 The fruits or pericarps which present trans- 

 verse dehiscence may be supposed to be formed 

 either of carpellary leaves in which the laminae 

 are articulated to the petioles, as in the Orange 

 {fig. 294), and which become separated at the 

 point of articulation, so that the imited petiole 

 part of the fruit, and the united laminae the upper 

 result from the prolongation and hoUowing out 

 of the thalamus, and the articidation of the car- 

 pellary leaves to its circumference, so that in 

 the dehiscence the lower part of the fruit is 

 formed by the concave thalamus, and the upper 

 part by the carpellary leaves ; thus resembling 

 the separation of the calyx in Eschscholtzia 

 from the thalamus. 



In the Monkey- pot {Lecythis) {fig. 671), the 

 lower part of the ovary is adherent to the tube 

 of the calyx, and the upper portion is free; -f^s'-eri.Prxisofthe 

 when dehiscence takes place, it does so in a mfoUaria), wmi 

 transverse manner and at the part where the transverse dehis- 

 upper free portion joins the lower adherent one, 

 so that it would appear as if the adherence of the calyx had 

 some effect in this case in producing the transverse dehiscence. 



Fig. 670. Fruit of Hen- 

 bane (Hi/oscyamus) 

 with transverse de- 

 hiscence. This fruit 

 is termed a pyxis, 

 •which Is a kind of 

 capsule. 



1 form the lower 

 or it may 



Fig. 671. 



