^ESTIVATION AND ITS TERMINOLOGY. 183 



one half exterior, and one interior or overlapped, the aestiva- 

 tion accords with £ phyllotaxy. When of eight or higher 

 numbers the spiral order is usually all the more manifest. 

 When of four or six, the case is one of whorls (opposite 

 leaves representing the simplest whorl), either of a pair of 

 whorls (as in Epimedium, Berberis, etc.), or a single whorl, 

 the parts of which have overlapped in cyclic order. 



(2) As to the terminology. Linnaeus in the " Philosophia 

 Botanica " treats only of vernation, there termed " Foliatio." 

 For this the former term was substituted, and that of aestivation 

 for the disposition of petals in a flower-bud, introduced, as I 

 suppose (not having the volume to consult), in the Termini 

 Botanici, published in the sixth volume of the " Amcenitates 

 Academicae," 1762. I refer to it only through Giseke's edi- 

 tion, 1781. Here the terms are convoluta, imbricata, condu- 

 plicata, defined only by reference to the section vernatio, arid 

 valvata, unhappily explained by a reference to the glumes of 

 Grasses, also " inaequivalvis ; si magnitudine discrepant." 

 Imbricata is the only term besides valvata which directly 

 relates to the arrangement of petals, etc., inter se ; and the 

 reference takes us back to something " tectus, ut nudus non 

 appareat," covered as with tiles, we may infer. In the " Phi- 

 losophia Botanica," under the section Foliatio, the definition 

 of imbricata is " quando parallele, superficie recta, sibi in- 

 vicem incumbunt." This would apply either to mode I, or 

 mode II, according as invicem is understood ; but the dia- 

 gram (tab. x. 6) shows that case I is intended. Convoluta 

 refers to the rolling of a petal or leaf by itself, as does con- 

 duplicata to its folding ; but Linnaeus gives two figures, one 

 of a single rolled-up leaf, the other of one leaf rolled up within 

 another. 



Finally, among the modes of vernation indicated by Lin- 

 naeus, there is one which it is important here to notice, relat- 

 ing as it does to the arrangement of a pair of leaves in the 

 bud, and evidently quite as applicable to a whorl of a larger 

 number of parts than two ; i. e. : 



" Obvoluta, quum margines alterni comprehendunt oppo- 

 siti folii marginem rectum " (Philosophia Botanica, 105). 



