Fig. 666. 



Fig. 556. 



DEHISCENT FRUITS. 307 



by giving way only on the margins within the sutures, where the 

 placentas are united ; and when the valves fall off, the placentas are 

 left in the form of three arched repla, or frames, to which the seeds 

 are attached. In the case of a free central placenta, when the valves 

 separate, it is sometimes diflBcult 

 to teU whether the dehiscence is 

 septicidal or loculicidal, inas- 

 much as there are no dissepi- 

 ments, and the placentas and 

 seeds form a column in the 

 axis. Their number, as well as 

 their alternation or opposition, 

 as compared with the sepals, will 

 aid in determining whether the 

 valves are the entire carpellary 

 leaves, as in septicidal dehis- 

 cence, or only halves united, as 

 in loculicidal dehiscence. In 

 some instances, as in Linum 

 catharticum, the fruit opens 

 first by loculicidal dehiscence, and afterwards the carpels separate 

 in a septicidal manner. 



Another mode in which fruits open is transversely, the dehiscence 

 in this case being called circumscissile (circum, around, and scindo, I 

 cut}. In such cases, the fruit or seed-vessel may be supposed to be 

 formed by a number of articulated leaves like those of the Orange, 

 the division taking place where the laminae join the petioles. In this 

 dehiscence the upper part of the united valves falls off in the form of 

 a lid or operculum, as in Anagallis (fig. 554), and in Henbane (Hyo- 

 scyamus), (fig. 555), and hence the fruit is often denominated operculate 

 (operculum, a lid). In some instances the axis seems to be prolonged 

 in the form of a hollow cup, and the valves appear as leaves united to 

 'it by articulation, similar to what occurs in the calyx of Eschscholtzia. 

 In Lecythis (the Monkey-pot) and in Couratari the calyx is superior, 

 and the lid is formed at the place where the calyx is attached. 



Transverse divisions take place occasionally in fruits formed by a 

 single carpel, as in the pods of some leguminous plants. Examples 



Fig. 664. Pyxidium or oapsiile of Anagallis arvensis, opening by eiroumsoissile dehis- 

 cence, c. Persistent calyx, p, Pericarp divided into two, the upper part, o, separating in 

 the form of a lid or operculum. On the capsule are seen three lines passing from the base 

 to the apex, and marking the true valves, g, Seeds forming a globular mass round a central 

 placenta. Fig. 555. Operculate capsule or pyxidium of Hyoscyamus niger, Henbane. 

 0, Operculum or lid separating and allowing the seeds to appear. Fig. 566. Lomentaceous 

 legume or lomentum (transverse sehizooarp) of Hedysarum coronarium. 1, Bntii'e, the 

 upper division being nearly detached from the rest. 2, Two of the joints cut longitudinally 

 to show the spurious loculaments, each containing a seed. This seed-vessel divides into 

 separate single-seeded poitions by solubility. 



