DICOTYLEDONES : POLYPETAL^ : THALAMIFLORJ:. 



603 



base of the stamens (Fig ^01 Bd). The ovary consists of two 

 carpels with the ovules in two longitadinal rows on the connate 

 margins of the carpels ; these two parietal placentte are connected 

 by a membranous growth which, as it is not formed of the margins 

 of the carpels, must be regarded as a spurious dissepiment (Figs. 

 407 D* E*v, 342 Civ). When the fruit opens, the pericarp splits 

 into two valves corresponding to the carpels, leaving their mar- 

 gins, as a frame or replurrij bearing the placentae with the spurious 

 dissepiment attached : the seeds remain attached to them for some 

 time (Fig. 342 C, p. 530). 



FiOi 407.— Flowers, fruits, and embryos of various Cruciferae. A Flower of Brassica (nat. 

 size) ; 8 pedicel ; fe fc calyx ; c corolla. B The same after removal of the perianth (much 

 mag.): a a the two outer short stamens ; b the four longer inner ones; /the ovary ; n the 

 Btigma; d gland. CSiliquaof Brassica: u dissepiment. D Augustiseptal siliculaof Thlaspi. 

 E Latiseptal silicula of. Draba. 1)* and JS* Diagrammatic transverse section of the preced- 

 ing : V dissepiment; 8 seed. F Indehidcent silicula of Isatis. G Jointed siliqua of Raphanus 

 Rnphanistrum : g style ; III separate segments. K-H Diagrams of differently-folded 

 embryos, with transverse sections : r radicles ; c c cotyledons. 



The flowers are in racemes in which the bracts are suppressed ; 

 when the lower pedicels are longer than the upper ones, the raceme 

 becomes a corymb, and then the lower flowers are usually zygomor- 

 l)hic, the petals turned towards the periphery being larger than 

 those directed towards the axis of the inflorescence, as in Iberis. 



The form of the fruit is of importance in the subdivision of this 

 order. In some genera it is much longer than it is broad, when it 



