132 VIGNETTES FROM NATURE. 



began to split up into two separate species. 

 The woodland loosestrife, remaining in damp 

 tree-covered spots, has most closely retained 

 the general appearance of the common ances- 

 tor, since its flowers are yellow, like those of 

 the other loosestrifes, and its capsule still 

 opens in longitudinal valves. The pimpernel, 

 on the other hand, growing in those bare 

 patches which human tillage renders so 

 common, has become a frequent weed of 

 cultivation over all Europe and half Asia, and 

 has accompanied man in his various migra- 

 tions throughout nearly the whole globe. 

 For some reason or other why, it is hard to 

 say it has found the transverse mode of 

 opening its capsule suit it better than the 

 valvular, perhaps because this plan saved its 

 seeds in some unknown way from some 

 dangerous animal foe ; and so it has univer- 

 sally adopted the new principle in place of 

 the old one. It has also changed the colour 

 of its flowers, through the selective action of 

 the fresh insect fauna to which it was exposed 



