PURPLE LOOSESTRIFE 



87 



The plant is 2-3 ft. hi\;h. It tlowt-rs in July and Aui^ust. It is a 

 herbaceous perennial, reproduced by ili vision, and olicn cultivated. 

 The (lowers are trimorphic, as noticed by Darwin or earlier by 

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

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

 the third case it is intc;rmcdialf, and lies Ijetween the two groups ot 

 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 

 beinsf oreen, belono- 

 ing to the stamens 

 of the lono- stvled 

 forms, the medium 

 to those ot the mid- 

 styled, and those 

 of the short -styled 

 forms have small 

 pollen -grains, which 

 are yellow. The an- 

 ther-stalks are pink 

 in the longer sta- 

 mens and uncoloured 

 in the shorter. 



It insects do not 

 visit it the plant 

 is sterile. But it is 

 visited by numerous 



bees, humble bees, and flies, which sctik- 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 -st\ led plants are 

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

 legitimately in two ways, antl illegitiniatelx' in four wa\s; and there 

 are 18 modes of union, 6 legitimate, 12 illegitimale, 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. 



Pholn. b. H.I 



plRPLK l.()()hK^>TRIFE (Lj'//iriuii Siiliciirin, I..) 



