360 



DICOTYLEDONES. 



There are two whorls of stamens, the external with introrse, and the internal 

 with extrorse anthers. The gynoeceum is often bi-carpellate (Fig. 354 D). 



The flowers may be considered as constmcted upon the monocotyledonous 

 type. Pterostegia has a perfectly monocotyledonous flower with 5 trimerous 

 whorls. Kheunt likewise, but here the external staminal whorl is doubled (Fig. 

 254 A). O&yria has a dimerous I?/eim-flower (4-leaved perianth, 6 stamens. 

 2 stigmas). Eumex has a J?/ie?tm-flower with the suppression of the internal 

 whorl of stamens (Fig. 354 B) ; Emex is a dimerous Rumex. Polygonum, to 

 which Coccolob -, Miililfnbeckia and others are related, differs from Rheum 



uiutra 



FIG. 355. Polygonum fagopymm : A branch with flower and Iruits (nat. size); B flower; 

 C the same in longitudinal section ; D anterior and posterior view of stamen ; E gynoeceum ; 

 F fruit (mag.) ; G fruit in longitudinal section; H transverse section, showing the curved 

 cotyledons embedded in the endosperm ; I the embryo. 



chiefly in having one of the leaves, which in the latter takes part in the forma- 

 tion of the perianth, developed in this case into a bracteole (so that the perianth 

 is reduced to rive members), and several or all the stamens in the inner whorl 

 become suppressed. The perianth in Coccoloba and Miihlenbeckia is more or 

 less perigyuous and becomes fleshy, enclosing the fruit. Miihlenbeckia 

 vlatyclada has flat branches with rudimentary leaves; sometimes branches 

 with normal, arrow-shaped leaves are found. Atraphaxis. 



