142 BOTANY. [CHAP. iv. 



terior stamen present in less highly evolved allied 

 plants being completely arrested, a single long style 

 divided at the tip lies along with the stamens under the 

 large arched upper lip. The two lips of the corolla 

 become joined together at some distance down, and 

 form a curved tube, at the bottom of which the nectar or 

 honey is secreted. The above type of corolla is called 

 bilabiate on account of the two prominent lips, and is 

 characteristic of the large natural order of plants called 

 Labiatce, but occurs also in allied orders of plants, as 

 the figwort order (Scrophulariacece), etc. The dead-nettle 

 flower is proterandrous ; the stamens become ripe in 

 pairs. The first pair when ready to shed their pollen 

 curve downwards from under the upper lip and place 

 their anthers in such a position that they come in con- 

 tact with the back of an insect visiting the flower for 

 nectar, the pollen being dusted on to the insect's back. 

 After the pollen is removed the anthers shrivel up and 

 disappear, the second pair in turn bending down into 

 the position previously occupied by the first pair. Finally, 

 after the second pair of stamens have had their pollen 

 removed and disappeared, the pistil curves down from 

 under the upper lip and places its stigmas in the posi- 

 tion previously occupied by the anthers, consequently a 

 bee on entering the flower with pollen on its back, 

 obtained from another flower, unconsciously effects 

 cross-fertilization by bringing the pollen in contact with 

 the stigma. 



The above arrangement for securing cross-fertiliza- 

 tion, although comparatively perfect in its way, is 

 eclipsed from every point of view by the contrivances 

 for this same object presented by the species of sage 



