2 20 THE PHYSIOLOGY OF PLANTS 



functions usually only as an attractive organ. If, however, 

 the calyx is only small, and the corolla undertakes the function 

 of protecting the sexual organs, as is the case in the flowers of 

 the Vine, then it is developed as rapidly as the calyx and pre- 

 cedes in its development all the other organs. 



On the other hand, it is rare for the calyx to undertake the 

 functions of the corolla. Instances of this have been mentioned 

 in the case of Aconitum and Delphiniujn. In some rare cases 

 the doubling of flowers depends upon this. Thus double 

 Primroses {Primula veris), Canterbury Bells {CamiMnula), and 

 Mimulvs become double by the transformation of the sepals 

 into petaloid leaves. 



But it most frequently is the case in doubling flowers that 

 the calyx remains unaltered and that the number of petals 

 increases very considerably. This may take place by the 

 transformation of stamens into petals, as it occurs, for instance, 

 in the Eanunculacese. The tendency to produce leaf-like organs 

 may, however, be so great that each stamenal rudiment divides 

 into several pieces, and each stamen will therefore be repre- 

 sented by several petaloid leaves {Caryophyllacece). Sometimes 

 the stamens remain unchanged, and tlien the rudiments of the 

 petals are formed of such a breadth that these leaves divide 

 up into several leaves, as happens often in the Fuchsia. When 

 the flowers of Clarkia become doubled, an actual proliferation 

 takes place at the base of the petaloid leaves formed from the 

 stamens. In some cases indeed such proliferation may occur 

 on the axis itself between the staminal whorl and the petals 

 {Campanula). 



In the case of Composites, the process of doubling is a 

 different one. What we generally call a flower is in this case 

 a basket-like head of flowers, i.e., a number of small distinct 

 florets, which with insufficient examination we should consider 

 as petals, are inserted on a cushion-like receptacle. The 

 florets may also be of two distinct kinds, as, for instance, in 

 the Cineraria, where the outer ones are brilliantly coloured, 

 the tube of the corolla being drawn out into a long tongue- 

 like structure formed by the fusion of the several petals {ray- 

 fiorets). The centre of the receptacle is occupied by incon- 

 spicuous tubular florets {dish-florets.) The so-called doubling 



