458 FOURTH GROUP.— SEED-PLANTS. 



be carefully distinguished from those in which the number of stamens is increased by 

 the branching of the original stamens, a proceeding which occurs in various divisions 

 of the Dicotyledons and is sometimes constant in entire families, as in the Dilleniaceae 

 (Fig. 402) and Tiliaceae (Fig. 403), where each group of staminal symbols in the 



diagrams belongs to an original stamen ; here the number of the original stamens 

 corresponds to that of the sepals and petals ; but the former may be fewer, as in 

 Hyperiaim perforatum with three bundles of stamens in a pentamerous flower, and 

 then a multiplication of the staminal filaments is combined with a diminution of 

 the typical number of the staminal leaves. 



Branching is much rarer in the carpels than in the stamens. It is very 

 distinctly shown in the Malvaceae where the typical number of the carpels is five, and 

 they are often so developed, as in Hibiscus ; but in many genera [Malope, Malva, 

 Althaea, etc.) five rudiments of carpels are first formed in the shape of slight pro- 

 tuberances, each of which soon gives rise to a larger number of outgrowths lying side 

 by side, and each of these produces a style and a one-seeded lobe of the peculiarly- 

 formed gynaeceum \ 



These few remarks will be sufficient to show what variations are possible in the 

 relations of number and position included under the formula Sn Pn St n { + ?i + . .) 

 Cn ( — ni), which, as has beeii already said, applies especially to flowers with 

 pentamerous and true tetramei ous whorls ; with the latter may be placed flowers like 

 Michauxia with octamerous whorls, and those with dimerous whorls, the (Enothereae 

 especially, and among these Epilobiuni with the formula S 2-\- 2 P x. 4 6"/ 4. 4C4, and 

 Circaea with the formula S 2 P 2 St 2 C 2 ; Trapa too with the formula ^"2 -f- aP x 4 

 ^/4 C2 should go with them. Though the calyx in Epilobiuni and Trapa is formed 

 of two whorls, this apparent whorl of two decussate pairs of sepals is followed by 

 the succeeding whorls exactly as if it were a true tetramerous whorl. But in 

 other dimerous and tetramerous flowers there is a more considerable variation, 

 inasmuch as two dimerous perianth-whorls developed like a tetramerous calyx are 

 succeeded by a staminal whorl, which is superposed on this pseudo-whorl composed 

 of two decussate pairs, as in Urtica and other Urticaceae and Proteaceae with the 

 formula S2-\-2 St 4 C\ (Fig. 282). 



Among the dimerous and trimerous flowers of the orders Polycarpicae and 

 Cruciflorae, where they are most perfectly developed, there is a tendency to devote 

 more than one whorl to the formation of each of the series of organs, calyx, corolla, 



Payer, Organogenic, Taf. 6- 



