432 FERTILIZATION AND FORMATION OF FRUIT IN PHANEROGAMS. 



Like the follicle, the Legume or Pod arises from a single carpel, but on ripening^ 

 it splits down both sutures completely to the base into two valves, which at the 

 moment of dehiscence become rolled up spirally. This type of fruit is extremely 

 common in the Leguminosae. As examples may be mentioned Lotus comiculatus 

 (fig. 325 ^) and the Senna (Cassia angustifolia, fig. 325 *). 



Dry dehiscent fruits, the product of two or more carpels, are termed capsules in 

 the restricted sense. We may distinguish several types of capsules; (1) such as split 

 into valves from the apex, as in the Birthwort {Aristolochia, fig. 325 ^), Rue {Ruta, 

 fig. 325^) and Violet {Viola, fig. 325''); (2) such as open by means of teeth restricted 

 to the apex, as in Caryophyllacese; (3) such as split longitudinally down the side- 

 walls, the actual cavities of the fruit opening, as in the Wood Sorrel {Oxalis, 

 fig. 325^); (4) such as produce several large apertures by the folding back of teeth, 

 as in the Snapdragon (Antirrhinum, fig. 325^); and (5) such as form numerous 



2 



I 



Fig. 326. — Achenes provided with a plume or pappus. 



1 Fruit of Valerian ( Valeriana officinalis). * The same in longitudinal section. 3 Fruit of the Artichoke {Cynara Scolymus)^ 

 (After Baillon.) 



small pores by the shrivelling of restricted areas, as in the Poppy (Papaver). The 

 capsules of the Cinchona-tree (Cinchona, fig. 325 ^°) split into two valves, which 

 remain attached at the apex, separating at the base only; whilst many capsules 

 dehisce transversely, a lid being removed, as in the Pimpernel (Anagallis, figs. 325 ^^ 

 and 325 ^^) and Eucalyptus (figs. 325 ^^ and 325 "). 



A special form of capsule, known as the Siliqua, is characteristic of most 

 Crucifers. It is usually described as consisting of two carpels, the exposed walls of 

 which come away, leaving a framework (the replum) to which the seeds are attached. 

 Stretched upon this framework is the membrane which formed the (" false ") parti- 

 tion of the ovary. This class of fruit is well shown in Honesty (Lunaria) and in 

 the Cabbage (Brassica oleracea, figs. 325 ^^ and 325 ^^). According to the termi- 

 nology given at p. 75 (4), the two valves which come away correspond to the two 

 outer non-ovule-bearing carpels, whilst the ribs which remain are the two inner 

 ovuliferous carpels. 



Though, in a great number of Angiosperms, the various floral -leaves disarticulate 

 and fall away after pollination and fertilization, this is not universally the case; in 

 a considerable number some of them remain behind, undergo various changes, and 

 form an outside investment or appendage to the fruit which plays an important 

 part in the dispersal or preservation of the seeds. The same is true of the bracts 



