100 



MORPHOLOGY OF THE ANGIOSPERMS 



ternating with the petals, diplostemonous, and the members of the 

 outer whorl opposite the petals, obdiplostemonous; where in more than 

 two whorls, polijstemonous (Fig. 47, A, B). Polystemonous androecia 

 are uncommon [four whorls in Lauraceae (Fig. 47B), several in 

 Aquilegia, Delphinium, Nandinn, Trochodendron; three in some species 

 of Illicium]; haplo- and diplostemonous are common. Obdiplostemonous 



Fig. 46. Diagrams of flower structure of Paeonia brownii, showing fascicled stamens. 

 A, showing trunk vascular supply to stamens; B, showing various degrees of con- 

 nation of stamens in fascicle, c, carpel; d, disc appendage; p, petal; sd, staminodia; 

 St, stamen; s, sepal. (A, from Eames, 1953.) 



androecia are characteristic of the Caryophyllaceae, Geraniaceae, 

 Oxalidaceae, Rutaceae, some Saxifragaceae, and some other taxa. 



Obdiplostemony represents an interruption in the usual sequence of 

 alternation in floral whorls; its morphological nature was much dis- 

 cussed in the 1870s and 1880s. Three interpretations of obdiplostemony 

 were proposed: that it arose by the addition of a new or extra whorl of 

 stamens (the intercalation theory); by the loss of a whorl between the 

 corolla and the androecium (the reduction theory); and by ontogenetic 



