ilSSTIVATION AND ITS TEEMmOLOGY. 55 



The type of the latter, and the common disposition when the parts 

 are live, is with two pieces exterior, the third exterior by one edge 

 and interior by the other, and two wholly interior. This is simply a 

 cycle in f phyllotaxy, the third piece being necessarily within and 

 covered at one margin by the first, while it is exterior to and with its 

 other margin covers the fifth, this and the fourth being of course 

 wholly interior. So, likewise, when the parts are three, one exterior, 

 one half exterior, and one interior or overlapped, the aestivation 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 Epimedmm, Berberis, 

 &c.), or a single whorl, the parts of which have overlapped in cyclic 

 order. 



2. As to the terminology. Linnaeus in the " Philosophia Eotanica " 

 treats only of Vernation, there termed Foliatio. For this the former 

 term was substituted, and that of astivation 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 Amoenitates " Academictio," 1762. I refer to it only through 

 Giseke's edition, 1781. Here the terms are convoluta, imlricata, 

 conduplicata, defined only by reference to the section vernatio, and 

 valvata, unhappily explained by a reference to the glumes of Grasses, 

 also '■' inrnquivalvis ; si magnitudine discrepant." Imbricata i9,i\iQou\Y 

 term besides valvata which directly relates to the arrangement of 

 petals, &c., inter se ; and the reference takes us back to something 

 •' tectus, ut nudus non appareat," covered as with tiles we may infer. In 

 the " Philosophia Botanica," under the section Foliatio, the definition 

 of imbricata is " quaudo parallele, superficie recta, sibi invicem incum- 

 bunt." This would apply either to mode I. or mode II., according 

 as invicem is understood ; but the diagram, tab. x., 6, shows that case 

 I. is intended. Convoluta refers to the rolling of a petal or leaf by 

 itself, as does conduplicata 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 Linnteus, 

 there is one which it is important here to notice, relating 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 oppositi folii 

 marginem rectum." " Phil. Bot.," 105. Or, in " Term. Bot.," _*' pagina 

 superiore lateribus approximatis ita ut alteram latus distinguat 

 alteram folium." 



This, as the definition and the diagram in the " Philosophia 

 Botanica" show, answers in aestivation to mode II. It was early 

 taken up as such by Mirbel (Elem. Phys. Veg. et Bot., 1815, ii., 738, 

 739), where the polypetalous corolla of Hermannia and Oxalis and 

 the gamopetalous corolla of Apocynea. are cited as examples. 



Valvate aestivation, our mode III., is rightly defined by Mirbel in 

 the same place, and still earlier by Brown. 



