GROUP V. ANGIOSPERMJE. 



451 



diplostemonous with regular alternation : in the comparatively 

 few trimerous flowers of Dicotyledons the dicyclic condition may 

 be observed in the androecium (Rheum, Polygonum, Berberis), or 

 in calyx, corolla, and androecium. The f- calyx, which is to be 

 found in very many Dicotyledons, may be regarded as equivalent 

 to a dicyclic calyx (see p. 446). A dicyclic gynseceum. is to be 

 found in a few Monocotyledons (e.g. Alisma, Butomus) and 

 Dicotyledons (e.g. Malvaceae such as Malva, Althaea, Lavatera). 



The conclusion to be drawn from these facts is that in the com- 

 plete dichlamydeous monoclinous flowers of Angiosperms there 

 are, as a general rule, five whorls of floral leaves ; the flowers are 

 pcntacyclic. In most Monocotyledons the five whorls belong, one 

 to the calyx, one to the corolla, two to the androecium, and one to 

 the gynseceum : in most Dicotyledons they belong, two to the 

 calyx, one to the corolla, one to the androecium, and one to the 

 gynseceum. 



If, now, such a pentacyclic flower with regularly alternating 

 whorls be taken as a type or standard of comparison, it will be 

 observed that many flowers deviate from it by having either a 

 larger or a smaller number of whorls, the deviation being combined 

 in some cases with direct superposition. 



Pleiotaxy, or an increase in the number of the whorls in a 

 flower, is characteristic of 

 a number of genera be- 

 longing to various natural 

 orders. Instances have 

 been mentioned above of 

 Monocotyledons and of 

 Dicotyledons having flow- 

 ers with a dicyclic gynse- 

 ceum, and of Dicotyledons 

 with a dicyclic corolla or 

 androecium : but the num- 

 ber of whorls is some- 

 times much greater (15 

 in Aquilegia), when the 

 flowers, as also the special 

 series, are said to be poly- 

 cyclic. Thus, the calyx 

 is polycyclic in Nandina 

 (Berberidaceee) ; the androecium, in Aquilegia, Rosa, and Papaver- 



Fie. 267. Floral diagram of Rota toriuntosa, 

 showing the polycyclic androecium and gynseceum. 

 (After Kichler.) 



