ANGIOSPERMS. 



349 



from those of the purely vegetative shoots. Hence to the eye alone the flower of the 

 Angiosperms appears a peculiar structure and altogether distinct from the rest of the 

 organism ; and this impression is heightened by the peculiar character of the floral 

 axis and especially by the presence of the floral envelopes, and above all by the 

 circumstance that the floral leaves are with few exceptions arranged in rosettes, even 

 when the leaves of the vegetative shoots 

 are placed singly and at a distance from 

 one another, or in two rows or in other 

 ways. Usually the perianth, the androe- 

 cium, and gynaeceum of the flower are 

 each composed of several members 

 arranged in concentric whorls or in 

 closely coiled spirals, one or more 

 whorls of perianth-leaves being suc- 

 ceeded by one or more whorls of 

 stamens, which are followed by the 

 gynaeceum in the centre of the flower ; 

 but sometimes one sometimes another 

 of these whorls may be absent, or 

 single whorls are represented by one 

 member only, as in Hippuris (Fig. 272), 

 where only one stamen and one carpel 

 are developed inside a small perianth ; 

 in rare cases the whole flower is re- 

 duced to a single sporophyll, as the 

 female flower of the Piperaceae and 

 the male and female flowers of some 

 Aroideae ; it much more often happens 

 that the whorls which follow one 

 another from without inwards (from 

 below upwards) are of the same 'num- 

 ber or are multiples of the same num- 

 ber^, and spread in every direction like 

 a rosette from a common centre, though 

 this character is often partially concealed by subsequent bilateral development and 

 by abortion. 



The floral envelope {perianth, perlgonc) is seldom entirely wanting, as in the 

 Piperaceae and many Aroideae ; it is more often simple, that is, it consists of one 

 whorl of two, three, four, five, or more rarely of more leaves (Figs. 267, 268) ; in this 

 case the perianth is often inconspicuous and composed of small green leaves, as in 

 the Chenopodiaceae and Urticaceae, but sometimes also large, of delicate structure 

 and gaily coloured (corolline), as in Aristolochta, Mlrabills'^ and some others. But 

 usually the perianth in both classes of Angiosperms is composed of two alternating 



Fig. 269. Inflorescence and flower of So/am, 

 the latter in longitudinal section 



' [This is symmetry in the sense of French and English botanical writers (see pp. 411, 423\] 

 '^ Mirabilis has what looks like a calyx, but the formation is rather of the nature of an involucre. 

 See p. 353. 



