II POLYGONACE^ 347 



R. sanguineus. — Schulz describes this species as 

 slightly protandrous ; Kerner as protogynous. Some 

 flowers have no pistil ; these may be on the same or on 

 special plants. The perianth bears only one tubercle, 

 which is bright red, and on the midrib of the upper- 

 most segment round the drooping fruit. 



R. conglomeratus. — In this species there are two 

 tubercles. 



R. maritimus is a local British plant. The flowers 

 are homogamous. 



R. Acetosella. — According to Lindman the flowers 

 early in the season are protogynous, the later ones 

 homogamous. Besides the complete, there are some 

 female dioecious flowers. 



Polygonum 



The species differ much in habit. Nectar is 

 secreted in some cases. Some species have cleisto- 

 gamous flowers. 



P. Bistorta (Bistort). — The flowers are protandrous. 

 Though small they are brightly coloured, and being col- 

 lected into a long spike are fairly conspicuous, and being 

 well supplied with nectar are much visited by insects. 

 The nectar is secreted by eight glands at the base of the 

 stamens. According to Schulz, besides the complete 

 there are also female flowers, which are more numerous 

 on the mountains than in the plains. The spike is 

 composed of small two -flowered groups — one flower 

 complete, the other male with a small style and rudi- 

 mentary ovary. The complete flowers open first, and are 

 protandrous. Gradually the anthers fall off', the styles 

 elongate, and the plant is adapted for fertilisation by 

 pollen from another flower. In the absence of insect 

 visits the anthers often touch their own stigmas. 



P. viviparum. — The length and relations of the 

 stamens and pistil diff'er considerably in diff"erent 

 districts. The plant does not set its seed easily, and is 

 principally increased by bulbils, into which the lower 

 and sometimes all the flowers are modified. 



