210 MANUAL OF BOTANY 



When one margin of each leaf overlaps the one next it, and 

 the other margin is overlapped by the leaf on the other side of 

 it, so that the whole whorl presents a more or less twisted ap- 

 pearance, the aestivation is contorted ; if the overlapping is con- 

 siderable, it is said to be convolute, as in the coroUa of the MaUow 

 {fig. 460). When the parts of a floral whorl are five in number, and 

 these arranged in such a manner.that there are two parts placed 

 on the outside, two inside, and the fifth overlappmg one of the 

 internal by one margin, while it is itself overlapped on its other 

 margin by one of the external parts, the sestivation is said to be 

 quincuncial {fig. 462). Familiar examples of this form are 



Fig. 461. Fig. 462. Fig. 463. Fig. 464. 



Fiff. 461. Diagram to illustrate imbricate estivation. The figures, 1, 2, 3, 4, 



5, show that the successiTe parts are arranged in a spiral manner. Fig. 



462. Diagram to illustrate quincuncial Eestivation. 1 and 2 are external, 



4 and 5 internal, and 3 is partly external and partly internal. Fig. 463. 



Diagram to illustrate cochlear Bestivation. Fig. 464. Diagram' to illus- 

 trate vexillaiy a3stivation. 1 and 2 form the al£e or wings, 3 and 5 the 

 carina or keel, 4 the vexillum. (See Fapitionaceous Corolla.') 



afforded by the corolla of the Rose and the calyx of the Bind- 

 weed {Convolvulus sepium). In this kind of sestivation a spiral 

 arrangement of the parts is well seen, and is indicated in the 

 diagram {fig. 462) by a dotted line. The spiral cycle thus 

 formed, which is the normal one in pentamerous or quinary 

 flowers (those with the parts in fives), and which occurs in the 

 majority of Dicotyledons, corresponds to the f, pentastichous, 

 or five-ra/nked arrangement of leaves. When instead of the 

 whoUy internal leaf being next to the whoUy external one it is 

 the next but one, a variety of estivation occurs to which the name 

 cochlear has been given {fig. 463). Familiar examples of this 

 are afforded by the Snapdragon {Antirrhinummaj us) and other 

 allied plants. Another marked modification of imbricated sesti- 

 vatjon occurs in the ooroUa of the Pea and other papilionaceous 

 flowers, where the superior petal 4, which is generally the largest, 

 and is called the vexillum, is folded over the others which are 

 arranged face to face {fig. 464). This kind of estivation is 

 commonly termed vexilla/ry. 



