132 



STRUCTUKAL BOTANY. 



[112, 113. 



336. Separately considered, we find each organ 

 here folded in ways similar to those of the leaf-bud ; 

 that is, the sepal or the petal may be convolute, invo- 

 lute, revolute, etc., terms already defined. Collectively 

 considered, the aestivation of the flower occurs in four 

 general modes with their variations the valvate, the 

 contorted, imbricate, and plicate. 



337. In valvate aestivation the pieces meet by their 

 margins without any overlapping; as in the sepals of 

 the Mallow, petals of Hydrangea, valves of a capsule. 



418 



^\/' 425 -^-^ 424 



418-426, Modes of aestivation. 424, Petals of the Wall-flower. 



The following varieties of the valvate .occur : Indupli- 

 cate, where each piece is involute i.e., has its two 

 margins bent or rolled inward, as in Clematis ; or redu- 

 plicate, when each piece is revolute having its mar- 

 gins bent or rolled outward, as in the sepals of Althea. 



338. Contorted aestivation is where each piece over- 

 laps its neighbor, all in the same direction, appearing 

 as if twisted together, as in Phlox, Flax, Oleander (421). 



339. Imbricated aestivation (imbrex, a tile) is a term 

 restricted to those modes in which one or more of the 

 petals or sepals is wholly outside, overlapping two 

 others by both its margins. This kind of aestivation 



