646 PHA NEROGA MS. 



but sometimes it is less (as in Hypericum perforalum with three staminal bundles 

 in the pentamerous flower); so that an increase in the number of stamens is 

 united with a decrease of the typical number of staminal leaves. 



The branching of carpels is much less common than that of stamens. It 

 occurs very clearly in Malvaceae, where the typical number of carpels is five, 

 and they are often developed as such (as in Hibiscus). In some genera however 

 (as Malva, Malope, and Althced) five original rudiments of carpels first of all make 

 their appearance in the form of a low cushion. Each of these forms very early 

 a larger number of outgrowths lying side by side, and each of these produces a style 

 and a one-seeded compartment of the peculiarly-shaped gynaeceum ^ 



This short sketch will be sufficient to show what variations are possible in 

 the numbers and positions of the parts that may be included under the expression 

 S^Pn'^UUn^" ) Cn (-m)j which, as has already been said, is especially characteristic 

 of flowers with pentamerous or truly tetramerous whorls. True tetramerous flowers 

 are allied not only to those that are octamerous (like Michauxia), but also to 

 those with dimerous whorls, among which (Enotherese may be especially men- 

 tioned. Of genera belonging to this family, Epilobium, for example, is constructed 

 on the formula ^92^2 ^X4 '^^4.4 Q> Circcea on that of S^ P^ Sl^ Q '■> ^^^ Trapa, with 



Fig. 461.— Diagram of CandolUa FIG. 462.— Diagram of Citrus FiG. 463.— Diagram of Tiliaceaj. 



(Dilleniaceae). (Aurantiaceje). 



the formula S^^^P^^^St^C^, must also be included here. Although in Epilobium 

 and Trapa the calyx really consists of two whorls, this pseudo-whorl formed of 

 two decussate pairs is followed by the other whorls exactly as if it were a true 

 tetramerous whorl. But other dimerous and tetramerous flowers exhibit a more 

 considerable deviation from the type, inasmuch as the two dimerous perianth-whorls 

 which develope as if they were a tetramerous calyx or corolla are followed by a 

 staminal whorl which is superposed on the pseudo-whorl consisting of two decussate 

 pairs, as in Urtica and other genera of the order, and in Proteaceae with the 

 formula ^2+2 ^^^^4 <^i (Fig- 37o)- 



Among the dimerous and trimerous flowers of the orders Polycarpae and 

 Cruciflorse, where they are the most perfectly developed, a tendency prevails for 

 more than one whorl to go to the formation of the calyx, the corolla, the androecium, 

 and even the gynaeceum, a tendency which may be expressed by the formula 

 »S'^(+p+...)^p(+iJ+---)'^^p(+Pt--")^i>(fz)4-"); for example, 



Fumariaceae, S^P^j^.^St^^.,. C^. 



Berberideae, 



Epimedivm, S^^^ P2+2 ^4+2 Q' 

 * See Payer, Organogenie de la fleur, PI. 6-8. 



