ESTIVATION. 



87 



interior and half exterior (3), and two wholly interior (4, 5), which are both nearest 

 to the top of the cone, and the most central. The Rose calyx (fig. 465) confirms this 

 view ; its outer sepals being next the axis of the flower, and consequently most 

 vigorously developed, present small lateral leaflets, and often a terminal true leaflet, 

 thus reducing the sepal to an unequally pinnate leaf like ordinary rose-leaves. As 

 the sepals rise in the quincunx, the growth becomes weaker, the third bears 

 small leaflets only on one side, and the upper or interior sepal terminates 



464. Quincunxial 

 aestivation. 



466. Papilionaceons 

 {estivation. 



467. Cercis. 



Flower with standard within 



the wings. 



468. Cochleate 

 asstivation. 



in a simple filament. The quincunx aestivation may be disturbed by unequal develop- 

 ment of the leaves of the whorl, and this especially occurs in the corolla, owing to 

 the relatively slow or rapid growth of some of the petals. Thus, in the papiliona- 

 ceous corolla (fig. 466), the standard, which represents No. 4 of the quincunx, and 

 ought to be internal, is wholly exterior, because, having developed more rapidly 

 than the other petals, it covers the two wings representing Nos. 1 and 2 ; this 

 aestivation is said to be papilionaceous (OB. vexillaris). In the St. John's Bread (Cercis), 

 the standard retains its normal position, and the quincunx is properly formed (fig. 

 467). In the Snapdragon (fig. 468) and other personate plants, the second petal is 

 interior instead of being exterior, either because it has developed before the others, 

 or because the latter have grown the most rapidly ; this mode of aestivation is called 

 cochleate (OB. cochlearis). The calyx has a similar arrangement. 



Amongst the varieties of imbricate aestivation is that termed convolute } (ce. con- 

 volutiva) : it occurs when the sepals or petals overlap, so that each completely 

 envelops all the others; as in the calyx of Magnolia, and the corolla of Poppies 

 (fig. 470). ^Estivation is alternate (ce. alternativa), when the leaves of the calyx 

 or corolla form two whorls, of which the exterior encloses the interior whilst 

 alternating with it, as in the calyx of the Wall/lower, and corolla of Fumitory 

 (fig. 472). _ 



[Estivation is straight (ce. recta), or open (ce. aperta), when the parts are so 

 little developed or so distant that they do not meet. ED.] 



SYMMETRY OF THE FLOWER. 



The term symmetry has been differently applied ; according to De Candolle, it 

 implies non- geometrical regularity in plants and animals ; other botanists distinguish 

 (often obscurely) symmetry from regularity: this we do not admit, but regard 



1 The term convolute is often used synonymously with contorted or twisted aestivation. 



