COROLLA 



59 



two {e.g. Poppy) or more whorls. In some flowers the petals 

 are spirally arranged — e.g. " Double Buttercups." 



When the perianth of a flower does not con- 

 sist of sepals and petals clearly distinguishable 

 from one another, but is composed of a single 

 whorl — e.g. Clematis — or a continuous spiral of 

 floral leaves, we assume that the corolla is 

 absent, and describe the flower as apetalous ; in 

 fact, we regard the single whorl or spiral of the 

 perianth as representing a calyx. To this rule 

 there are exceptions; as eixamples of which 

 plants belonging to the Daisy-family and Pars- 

 ley-family may be cited. Each flower of the 

 Parsley (compare fig. 183) has a calyx {cci) in the form of a small 

 green ring with five minute teeth; its corolla consists of five white 

 petals alternating with 

 the calyx-teeth. But the 

 flowers of some other 

 representatives of the 

 same family, though they 

 possess five white floral 

 leaves occupying the 

 same position with refer- 

 ence to the stamens and 

 carpels as in the Parsley, 

 yet have no appreciable 

 ring of teeth to corre- 

 spond with the calyx of 

 this plant. It is clear 

 that in this case the single 

 perianth-whorl of five white floral leaves represents the corolla, 

 and the calyx is absent. Similarly, in the Daisy-family, the 

 calyx is frequently small or absent (fig. 209). 



The chief function of the corolla is to render the flower 

 conspicuous so as to attract the notice of insects (see page 80). 

 When the flower does not profit by insect-visits the corolla is 

 small and inconspicuous, as in certain flowers of the Violet, 

 or absent, as in the Hazel. Even in cases in which the 

 visits of insects to a flower benefit the plant, the petals are 

 absent when the notice of the insects is sufficiently secured 

 by the attractive nature of conspicuous sepals {e.g. Clematis), 



Fig. .84. — Vertical section of flower of Potato : 

 c:ir=calyx; c(j = coroUa; a=anther; /£)=pores of 

 anther; ot= ovary; j^= stigma. 



