274 



PLANT STRUCTURES 



bilabiate structure (Fig. 210, c, d, e), and suggesting the 

 name of the dominant family. The upper lip usually con- 

 tains two petals, and the lower three ; the two lips are some- 

 times widely separated, and sometimes in close contact, and 

 differ widely in relative prominence. 



Associated with zygomorphy in this group is a frequent 

 reduction in the number of stamens, which are often four 

 (Fig. 212) or two. The whole structure is highly special- 

 ized for the visits of insects, and this great zygomorphic 

 alliance holds the same 

 relative position among 

 Sympetalae as is held 

 by the zygomorphic Le- 

 gumes among Archi- 

 chlamydeae. 



In the mint family, 

 as the Labiates are often 

 called, there are about 

 two thousand seven hun- 

 dred species, including 

 mint {Mentha) (Fig. 

 212), dittany (Cunila), 

 hyssop {Hyssopus), mar- 

 joram {Origanum), 



Fig. 259. Flowers of dead nettle (La- 

 mium) : A, entire bilabiate flower ; 

 B, section of flower, showing rela- 

 tion of parts.— After Warming. 



Fig. 260. A labiate plant (Teucrium), show- 

 ing branch with flower clusters (A), and 

 side view of a few flowers (B), showing 

 their bilabiate character.— After Briquet. 



