. FLOWER-BUD — ESTIVATION. 193 



rich colouring, and are apt to be confounded. In such cases, the term 

 Perianth (-Jrigl, around, S.\ihg, flower), or Perigone {iri^i, and yotij, 

 pistil) has been applied to avoid ambiguity. Thus, in the Tulip, 

 CrOeus, Lily, Hyacinth, authors speak of the parts of the perianth, in 

 place of calyx and corolla, although in these plants, an outer whorl 

 (calyx) may be detected, of three parts, and an inner (corolla), of a 

 similar number, alternating with them. Thus, the perianth of the 

 white Lily (Lilium album, fig. 284 p) consists of three outer parts, 

 ^e, alternating with three internal parts, 'pi, surrounding the essential 

 organs, e, the stamens, and s, the pistil. 



The term perianth is usually confined to the flowers of Mono- 

 cotyledons, whatever colour they present, whether green, as in Aspa- 

 ragus, or coloured; as in Tulip. Some use the term perianth as a 

 general one, and restrict the use of perigone to cases where a pistil 

 only is present. In some plants, as Nymphsea alba (fig. 342), it is 

 not easy to say where the calyx ends and the coroUa begins ; as these 

 two whorls pass insensibly into each other. 



Flowee-bud. — To the flower-bud, the name alabastrus (meaning 

 ros&iud) is sometimes given, and its period of opening has been called 

 anthesis (&v6rigig, flower opening), whilst the manner in which the 

 parts are arranged with respect to each other before opening is the 

 cestivation (cestiims, belonging to summer), or prcefloration (prce, before, 

 and flos, flower). The latter terms are applied to the flower-bud in 

 the same way as vernation is to the leaf-bud, and distinctive names 

 have been given to the difierent arrangements exhibited, both by the 

 leaves individually and in their relations to each other. Thus the 

 sepals and petals may be conduplioate, or they may be rolled outwards 

 or inwards in various ways, or may be folded transversely, becoming 

 cruTwpled or corrugated, as in the poppy. When the parts of a 

 whorl are placed in an exact circle, and are applied to each other by 

 their edges only, without overlapping or being- folded, thus resembling 

 the valves of a seed-vessel, the sestivation is valvate, as in the calyx of 

 Guazuma ulmifolja (flg. 285 c). The edges of each of the parts may 

 be turned either inwards or outwards ; in the former case, the sestiva 

 tion is induplicate, as in the corolla of Guazuma ulmifolia (fig. 285 

 p), in the latter- reduplicate, as in the calyx of Althsea rosea (figs. 

 286 c, 287 c). When the parts of a single whorl are placed in a 

 circle, each of them exhibiting a torsion of its axis, so that by one oJ 

 its sides it overlaps its neighbour, whilst its side is overlapped hi 

 like manner by that standing next to it, the sestivation is twisted or 

 contortive, as in the corolla of Althaea rosea (figs. 286 p, 288 p). This 

 arrangement is characteristic of the flower-buds of Malvaceae and 

 Apocynacese, and it is also seen in Convolvulacese and some Caryo- 

 phyUacese. When the flower expands, the traces of twisting often 

 disappear, but sometimes, as- in Apocynacese, they remain: 







