88 



FLOWER. 



[chap 



in size, form, and texture, from foliage-leaves to bracts may 



be very gradual, but in most 

 plants the transition is rather 

 abrupt. A ring or series of 

 numerous bracts, enclosing 

 flowers or pedicels, as in 

 Zinnia and Carrot, we have 

 called an involucre. In Mus- 

 tard the bracts are unde- 

 veloped : hence the flowers 

 are ebradeate. 



1 6. The organs of the 

 flower and their principal 

 modifications we ought now 

 to be tolerably familiar with 

 from schedule practice. There 

 are, however, a few charac- 

 ters of importance which 

 require further attention, ap- 

 particularly to the manner in which the parts of 

 the calyx and corolla are folded while in 

 bud (termed cEsiivation)^ to the form of the 

 corolla and the structure of the pistil. 



In the bud, the sepals and petals (or the 

 lobes of a gamosepalous calyx, or of a 

 gamopetalous corolla) may be folded with 

 their margins either more or less overlap- 

 ping, or simply in contact without over- 

 lapping. In the former case, the aestivation 

 is imbricate^ as in the corolla of Rose, 

 Dhak {Biitea), and Bignonia ; in the latter 

 valvate, as in the calyx of Clematis and the 

 corolla of Vine. Sometimes the calyx may be valvate and 

 the corolla imbricate, as in Hibiscus. 



U5. Dhak {Buteafrojidosa). 



plyinc 



Fig. 6i. Flower of 

 Grape-vine The 

 petalscaducoiis and 

 valvate in aestiva- 

 tion. 



