DOUBLE FLOWEES 



145 



morphologically : (1) stamens or pistils may change to petals 

 (Fig. 235); (2) adventitious or (iceessori/ petals ma if arise 

 in the circle of pet- 

 als. Both of these 

 categories may be 

 present in the same 

 flower, as in Figs. 

 233, 234, and 235. 

 lu the full -double 

 hollyhock, the pet- 

 als derived from the 

 staminal column are 

 shorter and make 

 a rosette in the cen- 

 ter of the flower. 

 Other modifications 

 of flowers are sometimes known as doubling. For ex- 

 ample, double dahlias (Fig. 232), chrysanthemums and 



sunflowers are forms in 

 which the disk flowers have 

 developed rays. The snow- 

 ball is another case. In the 

 wild plant (Fig. 236) the ex- 

 tei'iial flowers of the cluster 

 are large and sterile. In 

 t])(^ cultivated plant (Fig. 

 237) all the flowers have be- 

 come large and sterile. Hy- 

 drangea is a similar case. 



236. The wild or original form of the snowball. 

 Outer flowers larger. 



Review. — How do flowers 

 vary in form? How are the var- 

 ious parts determined iiv disguised 

 flowers? "What are 5-merong and 

 3-meron3 flowers? What are some of the common forms of gamo- 

 petalous corollas? Describe a labiate flower. Personate. Lily flower. 

 Papilionaceous flower. What are monadelpnous and diadelphous sta- 



237. CnlMv.atpd sTiowball, in which nil the 

 flowprs in the clnstor ha'.'<> hocome 

 larae and showy. 



