DOUBLE FLOWERS 



153 



263. Petals arising from the staminal column of holly 

 hock; and accessory petals in the corolla-whorl. 



of cultivation and increased food-supply, flowers tend to 

 become double. True doubling arises in two ways, morpho- 

 logically: (1) Petals 

 may appear in place 

 of stamens and pis- 

 tils; (2) adventitious 

 or accessory petals 

 may arise in the 

 circle of petals. Both 

 of these categories 

 may be present in 

 the same flower, as 

 in Fig. 263. In the 

 full-double holly- 

 hock, the petals de- 

 rived from the stam- 

 inal column are shorter and make a rosette in the center 

 of the flower. 



309. Other modifications of flowers are sometimes known 

 as doubling. For example, double dahlias (Fig. 257), chry- 

 santhemums and sunflowers are forms in which the disk 

 flowers have developed rays. The snowball is another case. 

 In the wild plant 

 (Fig. 264) the ex- 

 ternal flowers of 

 the cluster are large 

 and sterile. In the 

 cultivated plant 

 (Fig. 265) all the 

 flowers have be- 

 come large and 

 sterile. Hydrangea 

 is a similar example. 

 Double flowers are 



■ •I | , i , .. 264. The wild or orininal form of the snowball, 



likely tO be Sterile. Outer flowers larger. 



