DICOTYLEDONS. ^^^ 



reduced (if no further reference is made to the considerations mentioned above) to 

 the general formula which here assumes the simpler expression S,,P,^St,,C,^,^^. 

 A comparison with nearly-allied forms leaves little room for doubt that the vacant 

 spaces indicated by dots in the three outer whorls correspond to abortive members 



Fig. 4-'o.— Diagram of Aquilegia (Raiiunculaceae). 



in the sense already frequently indicated, even when the absence of these members 

 is so complete that even the earliest stages of development of the flower give no 

 indication of them. The same is the case also when the number of carpels' is less 

 than the typical one. Other cases however occur, as in the case of Rhus (Fig. 421), 



Fig. 421.— Diagram of Rhus (Anacardiacea;). 



Fig. 422.— Diagram of Cio2oi)Iiora (Euphorbiacere), a female, 

 b male flower. 



where certain members, in this case two out of the three carpels, disappear in the 

 course of development. Crozophora tmctoria (Fig. 422) is especially instructive in 

 regard to the relationships here suggested, the flowers becoming diclinous from 

 the stamens in the female flowers developing as sterile staminodes, which may be 



Fig. 423.— Diagram of pentainerous Ericacea; and Epacridere, 



Fig. 424.— Diagram of .-Esculus (Hippocastanea;). 



considered as the first step towards abortion, while in the male flowers the three 

 carpels are replaced by as many fertile stamens (Payer). 



Reference was made in the Introduction to Angiosperms (p. 481) to the inter- 

 position of a whorl of stamens between the members of a previously formed staminal 



