356 THE HIGHER DICOTYLEDONS. 



flowers ( \ in. across) and will serve as a type. It is perennial 

 and has slender branches, 8 to 24 ins. long, prostrate at the 

 base but soon becoming erect. 



Note the two opposite lines of hairs on the stem (cf . Chick- 

 weed) ; the opposite leaves, sessile or nearly so, to l ins. 

 long, cordate (heart-shaped), with deeply toothed margin 

 and wrinkled hairy surface. 



The flowers are in racemes, each of which arises in the axil 

 of one of the upper leaves, and is carried well up on a slender 

 axis ; the raceme with its stalk is 2 to 6 ins. long. Each 

 flower arises in the axil of a narrow pointed bract; these 

 are arranged spirally on the raceme axis, not in crossed pairs 

 like the foliage-leaves. 



Note the calyx, deeply divided into four narrow green 

 pointed lobes. The short flower-stalk is slightly curved, so 

 that the flat spreading lobes of the corolla lie in a vertical 

 plane ; what advantage do you see in this ? The plant com- 

 monly grows on hedgebanks, in which case the flowers all 

 tend to face outwards (why ?) ; when in open places, the 

 flowers face in different directions all round. Note the four 

 lobes spreading from the short tube of the bright-blue 

 corolla; the two side lobes, which lie behind (below) the 

 upper lobes, are similar in size and shape the upper lobe is 

 the largest, the lower lobe is the narrowest. 



Note the white rim (honey-guide) at the mouth of the 

 corolla-tube and the hairs which protect and partly conceal 

 the honey, secreted by a ring-like nectary round the base of 

 the ovary. 



The position of the lobes of the calyx and corolla suggests 

 that the uppermost (posterior) sepal of the calyx is missing, 

 and that the upper petal represents the two upper petals 

 usually found in this family ; occasionally one finds Speed- 

 well flowers with five sepals and five petals. The two stamens 

 present belong to the upper pair; each is inserted on the 

 corolla- tube between the upper petal and one of the side 

 petals. The ovary is two -celled, each cell having numerous 

 ovules on an axile placenta, and is broader than long (flat- 

 tened from side to side), covered with hairs, and notched at 

 the top, the style arising from the notch. 



The flowers are largely visited by hoverflies (Art. 292), and 

 appear to be specially adapted for cross-pollination by these 



