284 THE FLOWER. 



Geranium, and in many other cases (as in Fig. 280), we find the 

 prevailingly contorted or convolute aestivation affecting casual tran- 

 sitions to the imbricative mode, corresponding to those already 

 mentioned in the foregoing paragraph. 



499. The valvular or valvate estivation is that in which the parts 

 of a floral verticil are placed in contact, edge to edge, through- 

 out their whole length, without any overlapping (as in Fig. 355, 

 and the calyx in Fig. 356). Here the members of the circle are 

 strictly verticillate, and stand in an exact circle, no one being in 

 the least degree lower or exterior. The edges of the sepals or 

 petals in this case are generally abrupt, or as thick as the rest of 

 the organ, as is shown in the calyx of the Linden (Fig. 306) ; by 

 which mark the valvate aestivation may commonly be recognized 

 in the expanded flower. The several parts being all developed 

 under precisely similar conditions in this and the foregoing modes 

 of aestivation, these are naturally and almost without exception re- 

 stricted to regular flowers alone. 



500. By the inflexion of the edges, the strictly valvate aestivation 

 passes by insensible gradations into the induplicate (490), as in the 

 calyx of some species of Clematis ; a mode which is carried to a 

 maximum in some species of Lysimachia (Fig. 356), where the 

 two edges of the same petal are brought into contact, so as to be 

 conduplicate. When the induplicate margins are inrolled, they 

 become involute (Fig. 357) in aestivation. On the contrary, the 

 valvate calyx of many Malvaceous plants and the corolla of the 

 Potato blossom have the margins projecting outwards into salient 

 ridges, or are reduplicate, in aestivation. 



501. The tube of a gamopetalous corolla occasionally exhibits 

 similar ridges or folds, whether salient (as in the bud of some 

 Campanulas, Fig. 362), or reentering (as in Stramonium) : this 

 gives rise to the plicative, plicate, or plaited modification of aesti- 

 vation. Where the plaits are folded round each other, in a convo- 

 lutive manner, the aestivation is sometimes termed supervolutive, 

 or supervolute, as in the Morning Glory (Fig. 363). 



502. The spire in imbricative aestivation, and the order of 

 overlapping in the contorted mode, may turn either from left to 

 right, or from right to left ; and the direction is often uniform 

 through the same genus or family, but sometimes diverse in differ- 

 ent blossoms on the same plant. In fixing the direction, we sup- 

 pose the observer to stand before the flower-bud. De Candolle, 



