210 ORGANOGEAPHY. 



390), in which case the flower is termed unisexual; and it is still 

 further characterised as staminate or male {fig. 390), when it 

 contains only an androecium, or pistillate, carpellary^ or female 

 {fig. 389), when it contains only a gyncecium. 



2. JEstivation or Prcefloration. 



As the general arrangement of the rudimentary leaves of the 

 leaf-bud is called vernation (the spring state), so the mode in 

 which the diiFerent parts of the flower are disposed in the flower- 

 hud is termed their (Estivation (the summer state). The term 

 prcefloration is also sometimes used by botanists instead of 

 aestivation. The terms used in describing the various modiflca- 

 tions of sestivation are generally the same as those of vernation ; 

 but the former present some peculiarities, which renders it neces- 

 sary for us briefly to refer to their different arrangements. The 

 terms used in aestivation especially refer to the relative positions 

 of the component parts of the calyx and corolla, because the 

 stamens and carpels, from their peculiar forms, can give us no 

 such arrangements of their parts as are exhibited by the floral 

 envelopes. 



In describing the modifications of aestivation, we have, as in 

 the case of vernation, to include : 1st, the disposition of each of 

 the component parts of the floral envelopes, considered inde- 

 pendently of the others ; and 2nd, the relation of the several 

 members of either of the floral envelopes taken as a whole in 

 respect to one another. With regard to the disposition of each of 

 the component parts of the floral envelopes considered inde- 

 pendently of the others, the same terms are used as in those of 

 vernation, with the addition of the crumpled or corrugated form, 

 which is not found in the leaf-bud. This may be seen in the 

 petals of the Poppy {Papavcr) and Kock-rose {Helianthemiim); 

 it derives its name from the parts being irregiilarly contracted 

 into wi'inkled folds. 



With respect to the relation of the several members of either 

 of the floral envelopes taken as a whole to one another, various 

 forms occur, all of which may be arranged in two divisions ; 

 namely the Circular, and the Imbricated or Spiral. The former 

 includes all those forms in which the component parts of the 

 whorl are placed in a circle, and in nearly the same plane ; and 

 the latter those where they are placed at slightly different levels 

 in a more or less spiral manner, and overlap one another. 



1. Circular Mstivation. — We distinguish three forms of this, 

 i.e. the valvate or valvular; induplicative or induplicate; and 

 the reduplicative or reduplicate. The valvate aestivation {fig. 

 428), may be seen in the calyx of the Lime, and in Guazuma 

 ulmifolia. In this form the parts are flat or nearly so, and in 



