184 ESSA YS. 



Or, in Termini Botanici, " pagina superiore lateribus ap- 

 proximatis ita ut alterum latus distinguat alterum 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 Her- 

 mannia and Oxalis and the gamopetalous corolla of Apocynece 

 are cited as examples. 



Valvate aestivation, our mode III, is rightly defined by 

 Mirbel in the same place, and still earlier by Brown. 



Linnaeus made no use of aestivation as a character. Nor 

 did Jussieu, except merely that, in his " Genera Plantarum," 

 the petals of Malvaviscus are said to be convolute. 



In De Candolle's " Theorie Elementaire," 1813 — a still 

 unsurpassed treatise, upon which, next to the " Philosophia 

 Botanica," our botanical glossology rests — neither the word 

 aestivation, nor its synonym, prefloration, is mentioned, and 

 even vernation or prefoliation is equally omitted. 



But the history of aestivation as a botanical character be- 

 gan in a work published three years earlier, namely, in R. 

 Brown's " Prodromus Florae Novae Hollandiae," 1810. The 

 preface notes that it was first accurately observed by Grew. 

 In it Brown defines only the valvate mode, "ubi margines 

 foliolorum vel laciniarum integumenti invicem applicati sunt, 

 capsulae valvularum in modum." In the body of the work, 

 wherever it is important, the aestivation is noted as valvate, 

 imbricate, plicate, induplicate, etc. ; and the open aestivation 

 (aperta) is named by him in a subsequent paper. 



Being the first to employ aestivation systematically, and to 

 develop its value, Brown's terminology for its modes may well 

 be considered authoritative. And so indeed it is, as far as it 

 goes. But he did not make one important distinction, namely, 

 that between our I and II. Imbricate, in his use, comprises 

 all kinds of overlapping, that of the corolla of Apocynece and 

 of a Gentian, as well as that of a Primrose. He must have 

 not only noticed the difference, but also appreciated its gen- 

 eral importance, notwithstanding the occasional passage of 

 the one into the other. He must have also observed that in 



