194 BRITISH FLOWERING PLANTS chap. 



mentioned, devotes itself almost exclusively to L. Sali- 

 caria, whicli, however, is visited also by many otter 

 insects. Knuth suggests that the green colour of the 

 anthers of the longest stamens, which, of course, are 

 most exposed, serves perhaps as a protection against 

 pollen-eating insects. 



L. hyssopifolium. — This species is, according to Schulz, 

 protogynous. It is said by Vaucher, though Darwin 

 thinks erroneously, to be dimorphous. 



Peplis 



P. Portula (Water Purslane). — A small weak herb 

 growing in moist places. The very minute flowers 

 sometimes have no petals. 



CUCUEBITACE^ 



Our only representative is the common Bryony 

 {Bryonia dioica), which climbs by means of tendrils. 

 Honey is concealed in the flowers. The plants are 

 dioecious, the female flowers only half as large as the 

 male, in which two pairs of the five stamens are grown 

 together ; the fifth is free. The lower parts of the 

 calyx and corolla are grown together, and bear the 

 stamens, the bases of which completely cover the 

 stigma, leaving a passage, however, in the centre and 

 three at the sides which are protected by hairs. Lud- 

 wig records a case in which a female plant was fertilised 

 with pollen from a male growing at a distance of about 

 40 metres. One species of bee, Andrena Jlorea, appears 

 to visit this species exclusively. It has been suggested 

 that the flower may have some special odour, very 

 attractive to this particular bee, but which we cannot 

 perceive. Struck by the great attraction which these, 

 to our eyes inconspicuous, flowers have for insects, 

 Knuth suspects that they may possess some attraction 

 not visible to our eye, and suggests that they may emit 



