FLORAL FOEMS AND THEIR RELATIONS TO INSECTS 329 



/ 



FIG. 399. ^ESTIVATION OF FLOWERS. 



(a) Valvate. (6) Imbricate, (c) Contorted or 

 twisted. (</) Quincuncial. (/) Vexillary. 



arrangement of rudi- 

 mentary floral organs 

 in the bud is analogous 

 to the arrangement of 

 young foliage leaves; 

 and therefore that 

 what has been already 

 said on the subject of 

 prefoliation, or vernation, applies almost 

 equally to the subject of prefloration, or 

 aestivation. The word " aestivation " is 

 derived from the Latin ct'stas, summer, 

 this being the season when most flowers 

 begin to open, just as ' : vernation " is 

 derived from the Latin ver, the season 



specially associated with the expanding 

 of leaf-buds. Moreover, the terms which 

 are employed in describing the various 

 modifications in the one, answer almost equally for the other ; though 

 flower-buds exhibit certain arrangements which are peculiar, and for which 

 special terms have had to be invented. 



It is sufficient here to observe that 

 all the various modifications may be ar- 

 ranged under two heads, the circular and 

 the imbricated or spiral. The former 

 comprehends those varieties in which the 

 component parts of the whorl (the sepals 

 of the calyx, petals of the corolla, and so 

 forth) are arranged in a circle and nearly 

 on the same level ; and the latter includes 

 those forms in which the said parts over- 

 lap one another, and have a more or less 

 spiral arrangement, the consequence of 

 their being placed at slightly different 

 levels. For interesting varieties of circu- 

 lar aestivation the calyx of the flower-buds 

 of the Lime (Tilia) and Hollyhock (Althoea 

 rosea) and the folded corolla of the Potato 

 (Solanum tuberosum) may be profitably 

 examined; while the Camellia, Rose, Bind- 

 weed (Convolvulus), Snapdragon (Antir- 

 rhinum), and St. John's Wort (Hypericum) 

 offer examples of the chief varieties of FlG " 400 -- FLORET OF DANDELION. 



.... . or ._ , nn ~.^ (a) Cohering anthers, (ft) Extremity of style. 



spiral aestivation (figs. 39o and 399). (<> uguiate corona. 



