GROUP IV. PHANEROGAMIA : ANGIOSPERM^E. 



503 



due to the polycyclic development of the corolla, the additional 

 whorls being either new formations, or the result of the more or 

 less complete replace- 

 ment of the sporophylls 

 bj petals. 



An important case is 

 that to be found in 

 several Dicotyledonous 

 orders (Ericaceas, Fig. 

 455, p. 655, Pyrolaceee, 

 Crassulaceae, Fig. 318, 

 Saxif ragacea?, some 

 Caryophy llacene, Fig. 

 317; Onagraceae, Fig. 

 323 ; GeraniaceoD, Ox- 

 alidacese, Zygophyllacese, 

 Rutacea3, Fig. 317 0) 

 where the flower is diglo- 

 stemonous, and the 

 andrcecium is apparently dicyclic : but the flower is not simply 

 diplostemonous (as in the Monocotyledons), because the whorls do 

 not alternate regularly; the stamens of the apparently outer whorl 

 are directly antipetalous, consequently the stamens of the inner 

 whorl are antisepalous, and the carpels (in eucyclic flowers) are 

 antipetalous. Such flowers are said to be obdiplostemonous (Fig. 

 317 0). 



A variation of the typical obdiplostemonous flower is found in certain Caryo- 

 phyllacese (e.g. Viscaria, Fig. 317 A ; Lychnis, Cerastium, some species of 



O 



FIG. 316. Floral diagram of Rosa tomentosa, show, 

 ing the polycyclic androecium and gynaeceum. (After 

 Eichler.) 



A B C 



Fio. 317. Floral diagrams of two Caryophyllaceous flowers illustrating two forma of 

 obdipiostemony : A (Viscaria vulgaris) with antisepalous carpels: B (Spergula arvensis) 

 with antipetalous carpels (after Eichler) : C diagram of obdiplostemonous flower of 

 Dictamnus. 



