AESTIVATION, OR PR^EFLORATION. 



139 



aestivation ought to bear is not yet well settled, but that of con- 

 volute, here preferred, will probably prevail. 1 



259. In recapitulation, these principal forms of the aestivation 

 of floral circles may be classified in a synopsis. The}' are : I. 

 those not closed = open or indeterminate : II. closed ; and these 

 1, with the margins not overlapping = valvate ; 2, with margins 

 overlapping ; , one or more with both margins covered = imbri- 

 cate ; b, all with one margin covered, the other uncovered = 

 convolute. 



260. Plicate or Plaited, when applied to the flower-bud as a 

 whole, is in a somewhat different category. The term is here 

 used for the plaiting 



of a tube or cup, 

 composed of a circle 

 of leaves combined 

 into one body. It 



is well marked in 265 see 



the corolla of Convolvulus and of Datura, and 

 in most of the order to which these belong. In 

 Campanula, these plaits are all outwardly sa- 

 lient and straight (Fig. 265) ; in the corolla of 

 most Gentians, the plaits are internal and straight. 

 In Convolvulus and Datura (Fig. 266-268), 

 the narrow plaits overlap one another in a con- 

 volute way, when they are said to be Supervolute. 

 In the common Morning Glory and some other 

 species of Ipomoea, these plaits are besides spirally twisted or 



1 See article entitled " ^Estivation and its Terminology," above referred to. 

 The earliest name is Obvolute, given by Linnaeus to the kind of vernation in 

 which two leaves (conduplicate ones in his diagram) are put together so 

 that one half of eacli is exterior, the other interior. That is just the mode 

 in question reduced to a single pair of leaves, as it is in the calyx of a Poppy. 

 Mirbel is the only botanist who has applied the term to aestivation, and to a 

 circle of more than two leaves, and it has never been adopted in botanical 

 descriptions. It has the disadvantage that the prefix ob to botanical terms 

 means obversely or inversely. Contorted (contorta), in English Twisted, is in 

 early and is the commonest use, and it is sometimes expressive. The objection 

 to it is, that contortion or twisting of the flower-bud often conspicuously oc- 

 curs where there is no overlapping of edges (as in many species of Ipomoea) ; 

 that really no twisting accompanies the overlapping in a majority of cases 

 of this aestivation ; and that when there is a twisting it is not rarely in the 

 direction contrary to the overlapping; so that the contortion needs to be 



FIG. 265. Cross section of the extrorsely plicate or plaited tube of the corolla of 

 a Campanula in the bud. 266. Same of a Convolvulus (Calystegia), the plaits convolute 

 or supervolute. 



FIG. 267. Upper part of unexpanded corolla of Datura; the plaits convolute or 

 supervolute. 268. Cross section of the same. 



