MORPHOLOGY OP REPRODUCTIVE ORGANS 209 



1. Varieties of Circulwr Estivation. — We distinguish three 

 well-marked varieties of circular sestivation, i.e. the valvate, in- 

 duplicate, and reduplicate. The valvate {fig. 457) may be seen 

 in the calyx of the Lime, and in that of Quazuma uhrdfolia ; in 

 this variety the component parts are flat or nearly so, and in 

 contact by their margins throughout their v?hole length without 

 any overlapping. This variety of cestivation may be generally 

 distinguished, even when the flowers are expanded, by the 

 margins of its component parts being slightly thickened, or at all 

 events not thinner than the rest of the organ ; whereas in all 

 varieties of imbricated aestivation the overlapping margins are 

 usually thinner, as may be well seen in the sepals of the species 



Fig. 457. Fig. 458. Fig. 459. Fig. 460. 



Fnj. 457. Diagram to illustrate valvate aBstivatiou. Fig. 458. Diagram to 



illustrate indupllcate estivation, Fl>j. 459. Diagram to illustrate redu- 

 plicate Eestivatioa. Fig. 460. Diagram to illustrate contorted or twisted 



aestivation. 



of Geranium. "When the component sepals, or petals, instead 

 of being flattened, are folded inwards at the points where they 

 come in contact, (fig. 458), the aestivation is induplicate, as in 

 the petals of G-uanuma ulmifolia, and in the sepals of some 

 species of _ Clematis. When the margins are turned outwards 

 under the same circumstances {fig. 459), the aestivation is re- 

 duplicate, as in the sepals of the Hollyhock {Althcea rosea), 

 and some other Malvaoeous plants ; also in the petals of the 

 Potato. 



2. Varieties of Iitibricated or Spiral Mstivation. — We dis- 

 tinguish five varieties of this kind of aestivation, i.e. the hnhri- 

 cate, convolute, quincuncial, cochlear, and vexilla/ry. The 

 true imbricate aestivation, as seen for instance in the calyx, of 

 Camellia japonica {fig. 461), is formed by the. component parts 

 overlapping, each other more or less by their.margins like the tiles 

 on the roof of a house. Usually, when there are five leaves 

 in the florail whorl, one is overlapped on both margins, the next 

 one is completely external, and each of the other three overlaps 

 the leaf next it on one side and is overlapped by that, next it on 

 the other. 



