80 



AESTIVATION. 



251 250 249 



244-251, Modes of aestivation. 250, Petals of the wall-flower. 



389. CONTORTED AESTIVATION, where each piece overlaps its neigh- 

 bor, all in the same direction, appearing as if twisted together, as in 

 Phlox, flax, oleander. (247, 252.) 



390. 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 naturally results from the spiral arrangements so common in 

 phyllotaxy, while the valvate and contorted seem identified with the 



opposite or whorled arrange- 

 ment. The principal varieties 

 are 



391. THE QUINCUNTIAL, 

 consisting of five leaves, two 

 of which are wholly without, 

 two wholly within, and one 

 partly both, or one margin out, 

 the other in, as in the rose 

 family (248). This accompa- 

 nies the two-thirds plan in 

 phyllotaxy, and corresponds 

 precisely with it, each quin- 

 cunx being in fact a cycle 

 with its internodes suppress- 

 ed. ( 232.) 



392. THE TRIQUETROUS, 

 consisting of three leaves in 



252, Gossypium herbaceum, the cotton plant. Petals each set, one of which is Ollt- 

 contorted. . . . 



side, one inside, and the third 



partly both, as in tulip, Erythronium, according to the one-third plan 

 in phyllotaxy. 



