212 



ORGANOGRAPHY. 



true imbricate aestivation, as seen for instance in the calyx of 

 Camellia japonica {fig. 432), is formed by the parts being placed 



Fig. 431. Fig. 432. Fig. 433. Fig. 434. 



#000 



Fig. 431. Diagram to illustrate contorted or twisted apstivation. Fig. 



432. Diagram to illustrate imbricate sestivatiou. The figures 1,2, 3, 4.5, 

 show that the successive parts are arranged in a spiral manner.- Fig. 



433. Diagram to illustrate quincuncial aestivation. 1 and 2 are excernal, 

 4 and 5 internal, and 3 is partly external and partly internal. — -Fig. 

 4.34. Diagram to Illustrate cochlear aestivation. The part marked 2 in 

 the preceding diagram is here wholly internal instead of external as in 

 the quincuncial arrangement. The dotted line marked 2, indicates its 

 normal position in the imbricate form of aestivation. 



at different levels, and overlapping each other more or less by 

 their margins like the tiles on a house, the whole forming a 

 spiral arrangement. It is a very common form of aestivation. 

 When the parts, instead of merely overlapping, completely en- 

 velope each other, as in the calyx of Magnolia grayidiflora, and in 

 the corolla of Camellia japonica, the aestivation is termed con- 

 volute by some botanists ; but this term is now more frequently 

 applied to the contorted form of aestivation, when the parts 

 overlap to a considerable degree as in the Wallflower. When 

 the parts of a floral whorl are five in number, and these imbri- 

 cated in such a manner that there are two parts phiced on the 

 outside, two inside, and the fifth overlapping one of the internal 

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

 by one of the external parts, the aestivation is said to be q7un- 

 cuncial {fig. 433). FamiHar examples of this form are afforded 

 by the corolla of the Rose, and the calyx of the Bindweed 

 (Calystcgia sepiit7n). In this form of aestivation the spiral 

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

 diagram {fig. 433) by a dotted line. The spiral cycle thus 

 formed, which is the normal one in pe7itamerous or quinary 

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

 majority of Dicotyledonous plants, corresponds to the | ov jpen- 

 tastichous or five-ranked arrangement of leaves. When in a 

 quincuncial arrangement the second part of the cycle becomes 

 wholly internal, instead of being external as is ordinarily the 

 case, the regularity of the quincunx is interrupted, and a form 

 of aestivation occurs, to which the \\a.m.e cochlear has been given 

 ( fig. 434). Familiar examples of this form are afforded by 

 the Frogsmouth {Antirrhimim majus) and other allied plants. 



