I.] 



ONAGRACE/E. 



155 



(CEnothera biennis), hence called Evening Primrose : the 

 silky coma surrounding the top of the seeds of the 

 Willow-herbs. 



24. Natural Order Lythracese. The Lythrum 

 Family. 



DISTRIBUTION. Tropical and temperate regions of 

 both hemispheres ; most numerous in America. British 

 genera 2, species 3. 



Herbs. Flowers regular. Stamens 6 or 12. Ovary superior. 



Type Purple Loosestrife (Lythrum Salicarid]. 

 A perennial erect herb, with opposite or verticillate 

 entire leaves, and terminal spicate rose or purple flowers. 



OBSERVE the six teeth alternating with the free ex- 

 tremities of the coherent sepals, so that there appear to 

 be twelve sepals cohering to form the calyx : the relative 

 length of stamens and style in the Mowers of different 

 plants of Purple Loosestrife. Mr. Darwin pointed out 

 that the stamens in this species are of three lengths 

 long, medium, and short. But two lengths only occur on 

 the same plant, there being two sets of six in each flower. 

 The styles also are of three corresponding lengths long, 

 medium, and short ; and as they are never associated 

 with stamens of corresponding length, we have three 

 forms of flower : No. i,with short and medium stamens, 

 and long style ; No. 2, short and long stamens, and 



