Symmetry 177 



zygomorphic flowers are geotropic and will assume a definite position 

 with relation to gravity. 



In some cases certain flowers of an inflorescence are dorsiventral and 

 others radial. This is true of the ray florets of Compositae and of certain 

 Umbelliferae, where that part of the corolla directed toward the outside 

 of the head is much larger than that directed toward its center. In such 

 cases the entire inflorescence shows a radial symmetry. Here, again, the 



Fig. 7-15. Flower of Asphodelus. 

 Below, under normal conditions. 

 Above, after developing on a 

 clinostat. (From Vdchting.) 



whole pattern is symmetrical though certain of its elements are by them- 

 selves asymmetric. The situation may be still more complex. In some 

 Compositae there are as many as five types of fruits, as to size and shape, 

 formed on the head but showing symmetrical distribution (Pomplitz, 

 1956). 



Most inflorescences (like that described for Stellaria, p. 167) are radially 

 symmetrical, but some are definitely dorsiventral. A familiar example of 

 this is the heliotrope and its allies, where the flower cluster is one-sided 



