STRUCTURAL BOTANY. 69 



In tlie contorted and imbricated sorts, the segments of the 

 calyx, or the corolla, overlap each other, in the other two 

 thej do not. 



1. Yalvate jesttvatiox is that in which the pieces of a 

 perianth are brought in contact, edge to edge, throughout 

 their whole length, as the sepals of the Linden (see 

 Cut XIII., 1). Two varieties of valvate aestivation are 

 sometimes more obviously presented — namely : a, the i^e- 

 diiplicate, in which each piece of the circle has its two 

 edges bent outward, foraiing salient ridges, as in the 

 calyx of Mallows (Fig. 2), and h, the indujplicate, in which 

 each piece has its two edges bent inward, as in the calyx 

 of Clematis and the corolla of Solarium Uiberosum (Fig. 3). 



2. Plaited or plicate estivation, occurring in tubular 

 or gamopetalous flowers, is that in which the lobes of the 

 tube are folded lengthwise, so that the plaits turn either 

 outward, as in the corolla of Campanula, or inward, as in 

 that of Gentiana. The most remarkable variety of plaited 

 aestivation is the siipervolute^ in which the plaits are 

 wrapped round all in one direction, so as to cover each 

 other in a convolute manner, as in the corolla of Datura 

 Stramonium (Fig. 4 a cross-section, and Fig. 5 the upper 

 part of the corolla). 



3. Contorted, or convolutive estivation is that in 

 which every piece covers its neighbor by one of its edges, 

 all in the same direction, appearing, therefore, as if twisted 

 together, as in the corolla of Geranium (Fig. G). 



4. Imbeicated estivation is that in which one or more 

 pieces of a floral circle are wholly outside, and therefore 

 overlie and enclose the rest in the bud. There are two 

 principal varieties of this aestivation — namely, the trique- 

 trous and quincuncial. While the former has one piece 

 wholly outside (Fig- 7), there are two pieces outside in the 



