MONOCOTYLEDONS. 
625 
in large numbers to the margin of the leaf. These parallel transverse nerves are 
sometimes united into a lattice-like network by short straight anastomosings (as in 
Alisma, Cosius, and Ouinrandra, 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 
Fig. 426.— Diagram oi Scij-J>ics (Cyperacea;). FiG. 427.— Diagram of Iridea?. FiG. 428.— Diagram of Musacese. 
only in Alismacese and Juncaginese. The most common typical flora formula is 
therefore SnFnSf,i_^.n^n{+n)- It is only in the Hydrocharidese and a few other 
isolated cases that the number of whorls of stamens is larger. Where in other 
cases, as Bu/omus, 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 {ß^ St^^^ C.^, in only a very 
few cases scattered through the most different families {e.g. in Maianthemum and some 
Enantioblastae ; it is sometimes four or five (occasionally in Paris quadrifolia and 
Fig. 429.— Diagram of Zingiberaceae ; A Hedychuim (after Le Maout FiG. 430. — Diagram of Canna (Musaceae), after Payer, 
and Decaisne), B Alpinia (after Payer). 
in some Orontiacese) ; but the usual number of members in each whorl is three, 
and the typical formula therefore P^ -S/g^g C3(+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 andrcecium are present or only partially deficient, but are trans- 
^ The dimerous flower of Potamogeton (5'2 P2 «S'/j + 2 ^"4) (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 
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