THE FLOWER. 31 



Mixed inflorescence is that in which both the determinate and 

 indeterminate appear. In labiate plants the general inflorescence is inde- 

 terminate, while the separate heads are axillary cymes or fascicles. 



There are other altogether irregular forms of inflorescence, which, 

 however, do not require our attention. 



The floral organs comprise those which are essential to reproduction, 

 namely, stamens and pistils, and those which envelop the essential 

 organs, namely, calyx and corolla. All these organs are enfolded in the 

 bud, each kind in a separate whorl or circle by itself. 



The calyx is the external envelope of the flower. It is commonly 

 green, like the leaves, though occasionally colored (petaloid), and is com- 

 posed of from two to six or more leaflets, termed sepals, each separate 

 and distinct or all more or less united. 



FIG. 52. A polysepalous calyx. FIG. 53. A mono- or gamo- FIG. 54. Irregular (petaloid) 



sepalous calyx. calyx of aconite. 



When the sepals are distinct the calyx is termed polysepalous (Fig. 

 52) ; when they are united it is termed mono- or gamosepalous (Fig. 

 53). The monosepalous calyx is commonly more or less cut or divided 

 from the margin downward ; in such cases the undivided portion is termed 

 the tube, the free border the limb, and the point where these meet the 

 throat. The separate portions of the limb are often spoken of as lobes, 

 or teeth. It should be borne in mind, however, that in the early stage of 

 the development of the calyx the sepals are always distinct ; hence a 

 gamosepalous calyx is one in which the sepals have grown together, in 

 whole or in part, its teeth or lobes alone remaining to show the number of 

 the original sepals. 



The calyx is regular when its sepals are all alike (Figs. 52 and 53) ; 

 irregular when some of them are different in form from the others (Fig. 

 54). It is deciduous when it falls away after the fertilization of the 

 flower ; caducous when it falls as the flower expands ; persistent when 

 it remains until the fruit matures. 



The corolla is the inner floral envelope. It is commonly colored, 

 and in this respect is in strong contrast with the calyx. Its separate 

 leaflets are termed petals, and, like the sepals, they may be more or less 



