74 THE FLOWER. [CHAP. 



involucre. In Wallflower the bracts are undeveloped, 

 hence the flowers are cbracteate, 



1 6. The organs of the flower, and their principal modi- 

 fications, we ought now to be tolerably familiar with from 

 schedule practice. There are, however, a few characters 

 of importance which require farther attention, applying 

 particularly to the manner in which the parts of the calyx 

 and corolla are folded while in bud (termed astivatiori), 

 to the form of the corolla, and the structure of the stamens 

 and 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 over- 

 lapping, or simply in contact without overlapping. In 

 the former case, the aestivation is imbricate, as in the 

 corolla of Buttercup ; in the latter valvate, as in the 

 calyx of Clematis. Sometimes the calyx may be valvate 

 and the corolla imbricate, as in Mallow. 



17. The petals of a polypetalous corolla, if narrowed 

 to the base like those of the Wallflower or Pink, are 

 clawed, the narrow part being the claw, the expanded 

 part the lamina. In a gamopetalous corolla, or gamosep- 

 alous calyx, the lower united portion is called the tube ; 

 the free divisions, which indicate the number of parts 

 cohering, constitute the limb j the divisions of the limb 

 being spoken of simply as teeth if small, segments or lobes 

 if larger. The more important forms of the corolla are 

 noticed in Part II. under the groups of plants which arc 

 respectively characterised by peculiar modifications of it. 



18. When in our first chapter we spoke of all the 

 organs borne by the stem as leaves of some kind, you 

 were not in so favourable a position as, from subsequent 

 experience you must now be, to appreciate the broad 

 sense in which the word leaf was employed. I repeat, all 

 the organs borne by the stem and its branches are modi- 

 fications of one morphological leaf-type. By this state- 

 ment you are not to understand that a petal, or a stamen, 

 or a carpel, is a modified foliage -leaf, any more than that 

 a foliage-leaf is any one of these organs modified ; but 

 they are all alike modifications of one common leaf- type 

 which has only an ideal existence. Thus the leaf may be 

 an organ either for the purpose of nutrition, or of repro- 



