PURPLE LOOSESTRIFE 





The plant is 2-3 ft. high. It flowers in July and August. It is a 

 herbaceous perennial, reproduced by division, and often cultivated. 

 The flowers are trimorphic, as noticed by Darwin or earlier by 

 Vaucher. The stamens are in two groups, and in the one case the 

 stigma is projecting, in the other it is shorter or included, whilst in 

 the third case it is intermediate, and lies between the two groups of 

 anthers, and they may 

 thus be called long-, 

 short-, and mid-styled 

 forms. The ratio of 

 size of the seeds is as 

 100, 142, 121. The 

 pollen grains also 

 differ, the largest 

 being green, belong- 

 ing to the stamens 

 of the long- styled 

 forms, the medium 

 to those of the mid- 

 styled, and those 

 of the short -sty led 

 forms have small 

 pollen -grains, which 

 are yellow. The an- 

 ther-stalks are pink 

 in the longer sta- 

 mens and uncoloured 

 in the shorter. 



If insects do not 

 visit it the plant 

 is sterile. But it is 

 visited by numerous 



bees, humble bees, and flies, which settle on the stamens and pistil 

 on the upper side. Pollen to be fertile must be transferred to a 

 plant with flowers with the stigma at the level of the stamens from 

 which the pollen came, and when long- and short -styled plants are 

 crossed, the result is fertile seed. A single flower can be pollinated 

 legitimately in two ways, and illegitimately in four ways; and there 

 are 18 modes of union, 6 legitimate, 12 illegitimate, in the union of 

 three forms. Trimorphism may be advantageous. The chances are 2 

 to i in favour of forms being different and incapable of self-pollination. 





Photo. B. Hanley 



PURPLE LOOSESTRIFE (Ly thrum Saticaria, L.) 



