548 



PHANEROGAMS. 



with an equal number of members; viz. an outer and an inner perianth-whorl, 

 an outer and an inner whorl of stamens, and a carpellary whorl, which is succeeded 

 by a second carpellary whorl only in Alismaceae and Juncagineae. The most 

 common typical flora formula is therefore S^F^S/,,^nCn(+u)- It is only in the 

 Hydrocharideee and a few other isolated cases that the number of whorls of stamens 

 is larger. Where in other cases, as Butomus, an increase of the typical number 

 of stamens occurs, this takes place by de'donhlement without any increase of the 

 number of whorls (Fig. 400 A). 



The number of members in each whorl is two {S.^ P^ ^4+2 Q)' i^^ only a very 

 few cases scattered through the most different families {e. g. in P>Iaianthemum 

 and some Enantioblastce ; it is sometimes four or five (occasionally in Paris 



Fig. 395. — Diagram of Scirpus (Cyperacere). 



Fig. 396. — Diacjraui of Iridece. 



Fig. 397. — Diagram of Musaceie. 



quadrifolia and in some Orontiaceae) ; but the usual number of members in each 

 whorl is three, and the typical formula therefore ^3 Pg ^4^3 (73(^3) . In the large 

 section of Liliiflorse, in some Spadiciflorse, and in many Enantioblastae, Juncagineae, 

 and Alismaceae^ this typical floral formula is at once obtained empirically; but 

 in most others particular members or whorls are wanting; but the abortion of 

 these is generally at once evident from the position of those that are present. 

 In the Scitamineae with only one or even with only half an anther (Fig. 398, 399) 



Fig. 398.— Diagram of Zingiberaceas ; A Hedychium (after Le Maout 

 and Decaisne), B Alpinia (after Payer). 



Fig 399.— Diagram of Caima (Musacea-), after Payer. 



the rest of the members of the androecium are present or only partially deficient, 

 but are transformed into petaloid staminodes. It has already been pointed out 

 how the flowers of Gramineae and Orchideae can be traced back to the trimerous 

 pentacyclic type; the theoretical diagrams here given (Figs. 395-402) will answer 

 the same purpose for some of the other more important families. 



If the pentacyclic flower wdth the formula »S'„P^i67„^„ C„(^,j) is considered as 



^ The dimerous flower of Potamogelon {S.^P.,^St.^^C^) (see Hegelmaier, Bot. Zeit. 1870, p. 287) 

 differs from the typical formula only lo this extent, lliat the four carpels arise simultaneously, and 

 are placed diagonally to the preceding pairs. 



