Hi.] POLYGALACE^E. 69 



The few capsules which are produced when insects 

 are excluded are probably due to the curling up of 

 the petals (as Fermond and F. Miiller remark) as 

 they wither, by which process pollen-grains adhering 

 to the papillae may be inserted into the cavity of the 

 stigma. The moth Plusia is said to visit the flowers 

 largely. Humble-bees are common agents in fertil- 

 ising these flowers ; but I have seen more than once 

 a fly (Rhyngia rostratd) with the under side of its 

 body, head, and legs dusted with the pollen of 

 this plant, and having marked the flowers which 

 they had visited, found, after a few days, that they 

 had all been fertilised. 



" It is curious in this case, as in many others, how 

 long the flowers may be watched without seeing 

 one visited by an insect. During one summer, I 

 repeatedly watched some large clumps of heartsease, 

 many times daily, for a fortnight, before I saw a 

 humble-bee at work. During another summer I 

 did the same, and then one day, as well as on two 

 succeeding days, I saw a dark-coloured humble-bee 

 visiting almost every flower in several clumps ; and 

 after a few days almost all the flowers suddenly 

 withered, and produced fine capsules. A certain 

 state of the atmosphere seems to be necessary for 

 the secretion of nectar, and as soon as this occurs, it 

 is perceived by various insects, I presume by the 

 odour emitted by the flowers, and these are 

 immediately visited." 



POLYGALACE^E. 



This order contains, according to Bentham, but one 

 British species, which, however, is very common, the 



