v.] GALEOBDOLON, GALEOPSIS, STACHYS. 159 



lower bract of the flower above. According to 

 Delpino, Ajuga is proterandrous. The pistil is 

 already mature when the flower opens, but then lies 

 behind and is protected by the stamens. After a 

 while the stamens separate a little, so that the 

 stigma is in its turn exposed. In Ballota nigra 

 the arrangement of the stamens and pistils is 

 somewhat similar, and the flower is also slightly 

 proterandrous. 



In Galeobdolon luteum, the flower tube is eight mm. 

 (but, as the upper end is dilated, practically only 

 six mm.) in length. Though the stigmatic ends of 

 the pistil diverge shortly after the opening of the 

 flower, and appear to be then already mature, still 

 they occupy a more prominent position at a later 

 period. In this respect, therefore, it is intermediate 

 between Lamium and Ballota. 



Galeopsis tetrahit is a variable plant, and the tube 

 varies in length in different specimens from n to 17 

 mm. ; of which, however, the 4 6 upper millimetres 

 are somewhat expanded. This variability is an in- 

 teresting fact in relation to the theory of natural selec- 

 tion. The pistil, when mature, moves forward, as in the 

 preceding species. G. ochroleuca agrees very closely 

 with G. Tetrahit, but the tip of the pistil, instead of 

 lying between the anthers of the two longer stamens, 

 projects slightly beyond them. G. versicolor has a 

 longer tube, while G. Ladanum has a somewhat 

 shorter one ; in most respects, however, they agree 

 with G. ochroleuca. 



S tacky s sylvatica is distinctly proterandrous, but 

 has not lost the power of self-fertilisation. In S. 



