iv.] LYTHRARIE^E. 101 



L. palustris a minute marsh plant, hitherto found in 

 very few localities in Britain, though it ranges over 

 Central Europe, Asia, and North America. The 

 genus Circaea contains two species, C. alpina and C. 

 lutetiana, the Enchanter's Nightshade. This species 

 has two stamens, and as the flower is small, any 

 insect of moderate size would probably touch both 

 them and the pistil ; most likely, however, coming in 

 contact with the stigma first, as it projects rather 

 beyond the anthers. ' \\ 



LYTHRARIE^E. '*' 



This order contains two British genera, Ly thrum 

 and Peplis, the former of which is of peculiar interest 

 and has been already alluded to in the opening 

 chapter (antt p. 40). 



Lythrum salicaria (Fig. 77), presents us with 

 three distinct forms of flower, which were already 

 recorded by Vaucher, while their function* and 

 relations were first explained by Mr. Darwin. He 

 distinguished them according to the length of their 

 styles, as the Long-styled (Fig. 78), Mid-styled 

 (Fig. 79), and Short -styled (Fig. 80). In this 

 species it is remarkable that the seeds of the three 

 forms differ from one another; 100 of the long- 

 styled seeds being equal to 121 mid-styled, or 142 

 short-styled. The pollen grains, also, not only differ 

 in size, the long stamens having the largest pollen 

 grains, the middle-sized stamens middle-sized pollen 

 grains, and the short stamens small pollen grains ; but 

 also in colour, being green in the longer stamens, and 



