1932 



A TEXTBOOK OF THEORETICAL BOTANY 



insect working regularly up the spikes from below brings pollen from other 

 plants to the stigmas. Humble bees usually behave in this way, working 

 up from below rather than downwards from the top of an inflorescence. 



A B 



Fig. 1859. — Teuciium. Flowers to illustrate pollin- 

 ation. Sec in text. 



Automatic self-pollination can only occur if the change in position of stamens 

 and style takes place before all the pollen has been liberated. 



The Scutellarioideae are a small sub-family in which the most common 

 genus is Sciitellaria with 200 cosmopolitan species. S. galericulata and 

 S. tninor, the Skull Caps, are found in Britain. The flowers are paired in 

 the axils of the leaves, a feature which distinguishes this genus from the 

 rest of the family. 



The Lavanduloideae contain the single genus Lavandula with twenty 

 species distributed between the Mediterranean and India. From the 

 common species L. vera is obtained the Oil of Lavender, which is prepared 

 by the distillation of the flowers. The flowers are protandrous, nectar 

 being secreted in considerable quantities. Pollination is eflFected chiefly by 

 bees, but the flowers are also visited by long-tongued insects, particularly 

 by humming-bird hawkmoths. 



The Stachydoideae, as already pointed out, are a large sub-family em- 

 bracing a number of tribes. The inflorescence is made up of paired cymose 

 inflorescences each consisting in Salvia of a three-flowered dichasium, 

 or more generally branching and becoming modified into a pair of mono- 

 chasia. In either case the axes are contracted so that the flowers appear to 

 be produced in whorled clusters. The bracts may be simple or highly 

 differentiated, as in Monarda (Fig. i860). The flowers show considerable 

 variation, with corresponding difl'erences in the pollination mechanisms. 



