MOBPHOLOGY OF THE FEUIT AND SEED 257 



its two surfaces and nearly straight ; at other times, however, it 

 becomes spirally contorted so as to resemble a screw (fig. 557) 

 or a snail-shell, as in some species of Medicago (fig. 556) ; or 

 it is coiled up like a caterpillar, as in Scorpiurus sulcata (fig. 

 555) ; or curved like a worm, as in OcBsalpinia coriaria ; or it 

 assumes a number of other irregular forms. Certain deviations 

 from the ordinary structure of a legume are met with in some 

 plants ; thus, in Astragalus (fig. 422) and Phaca (fig. 423), it 

 is two-celled, in consequence of the formation of a spurious 

 dissepiment, which in the first plant proceeds from the dorsal 

 and in the latter from the ventral suture. In other cases a 

 number of spurious horizontal dissepiments are formed, by which 

 the legume becomes divided into as many cells as there are 

 seeds, as in Cassia fistula (fig. 417). Another irregularity also 

 occurs in the latter plant, the legume being indehiscent, though 

 the two sutures are clearly marked externally. Other indehiscent 

 legumes are also met with, as in Aracliis and Pterocarpus, in 

 which there is sometimes no evident mark of the sutures exter- 

 nally ; such legumes will, however, frequently split into two 

 valves like those of a pea, if a little pressure be applied as in the 

 ordinary process of shelling peas. 



3. The Lomentum,. — This is a kind of legume which is con- 

 stricted in a moniliform manner between the seeds, as in Hedy- 

 sariim, (fig. 529), Ornitliopus, and Acacia SopJiora (fig. 558). 

 It is sometimes called a lojnentaceous legume. This fruit, 

 together with the leguni^ characterises the plants of the 

 Leguminosse. When th^omentum is ripe, it commonly sepa- 

 rates into as many pieces as there are constrictions on its surface 

 (fig. 529), or it remains entire (fig. 558) ; in the latter case the 

 seeds are separately enclosed in cavities which are formed by the 

 production of as many internal spurious dissepiments as there 

 are external constrictions. 



Dehiscent Polycarpellary Fruits. 



1. The Capsule is a superior, one- or more celled, many- 

 seeded, dry, dehiscent fruit. The dehiscence may either take 

 place by valves, as in Colchicum (fig. 513) and Datura (fig, 521) ; 

 or by pores, as in the Poppy and Antirrhinum (fig. 429) ; or 

 transversely, as in the Pimpernel (fig. 560) and Henbane (fig. 

 527) ; or only partially, as in Mis;norette (fig. 509), DiantJius 

 (fig. 508), and Lychnis (fig. 507). When the capsule dehisces 

 transversely the iruit has received the distinctive name of Pyxis. 



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