METAMORPHOSIS OP THE FLOWER. 



113 



rieties of the valvate occur: In-duplicate, where each piece is in- 

 volute i. e., has its two margins bent or rolled inward, as in 

 Clematis , or reduplicate, when each piece is revolute having 

 its margins bent or rolled outward, as in the sepals of Althea 

 rosea (419, 420). 



338. Contorted aestivation is where each piece. overlaps 

 its neighbor, all in the same direction, appearing as if twisted 

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



418 



425 



418-425, Modes of aestivation. 424, Petals of the Wall-flower. 



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

 stricted 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 ai-rangements so common in phyllotaxy, while the valvate 

 and contorted seem identified with the opposite or whorled ar- 

 rangement. The principal varieties are the following : The Quin- 

 cuncial, consisting of five leaves, two of which are wholly with- 

 out, two wholly within, and one partly both, or one margin out, 

 the other in, as in the Rose family (422). This accompanies 

 the two-fifths cycle in phyllotaxy, and corresponds precisely 

 with it, each quincunx being in fact a cycle with its internodes 

 suppressed. (See fig. 300, and 266.) The Triquetrous, con- 

 sisting of three leaves in each set, one of which is outside, one 

 inside, and the third partly both, as in Tulip, Erythronium, 

 agreeing with the two-thirds, or Alder Cycle ( 265). The Con- 

 volute, when each leaf wholly involves all that are within it, as 



