MONOCOTYLEDONS . 



625 



in large numbers to the margin of tlie leaf. These parallel transverse nerves are 

 sometimes united into a lattice-like network by short straight anastomosings (as in 

 Ali'sma, Cos/us, and Ouzn'randra, the mesophyll being absent within the meshes of 

 the latter). It is only rarely (as in some Aroideae) that projecting lateral veins 

 are given off from the mid-rib, a finer reticulated venation springing from them. 



The Flower of Monocotyledons usually consists of five alternating isomerous 

 whorls ; 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 



FIC. 426.— Diagram oi Scirpus (Cyperacese). 



Fig. 427.— Diagram of Iridere. 



Fig. 428.— Diagram of Musaceae. 



only in Alismacese and Juncagineae. The most common typical flora formula is 

 therefore S^Pn^ln^n^ni^-n)- It is only in the Hydrocharideae and a few other 

 isolated cases that the number of whorls of stamens is larger. Where in other 

 cases, as Bulomus, an increase of the typical number of stamens occurs, this takes 

 place by dedouhlement without any increase of the number of whorls (Fig. 431 A). 



The number of members in each whorl is two {S^ P^ 8/^+2 C^), in only a very 

 few cases scattered through the most different families {e.g. in Maianthemiim and some 

 Enantioblastae ; it is sometimes four or five (occasionally in Paris quadrifolia and 



FIG. 429.— Diagram of Zingiberaceae ; A Hedychmm (after Le Maout 

 and Decaisne), B Alpinia (after Payer). 



Fig. 430. — Diagram of Catma (Musaceae), after Payer. 



in some Orontiacese) ; but the usual nymber of members in each whorl is three, 

 and the typical formula therefore S^ P^ St^^^ ^(+3)- In the large section of Lilii- 

 florae, in some Spadiciflorae, and in many Enantioblastae, Juncagineae, and Alis- 

 maceae ^, this typical floral formula is at once obtained empirically ; 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. 429, 430) the rest of the 

 members of the androecium are present or only partially deficient, but are trans- 



^ The dimerous flower of Po^rtmoo-e/o« {S^P^St^^ ^C^ (see Hegelmaier, Bot. Zeitg. 1870, p. 287) 

 differs from the typical formula only to this extent, that the four carpels arise simultaneously, and 

 are placed diagonally to the preceding pairs. 



s s 



