POLYGON ACE AE 



343 



2472. P. Bistorta L. (Ricca, Atti Soc. ital. sc. nat., Milano, xiv, 187 1, p. 3 ; 

 Herm. MuUer, ' Fertilisation/ pp. 511, 516, ' Weit. Beob.,' II, p. 221, 'Alpenblumen,' 

 p. 179; Schulz, * Beitrage/ I, p. 95 ; Warnstorf, Verb. bot. Ver., Berlin, xxxviii, 1896 ; 

 Kerner, ' Nat. Hist. PI.,' Eng. Ed. i, II, p. 327 ; Knuth, ' Bloemenbiol. Bijdragen.') 

 The flowers of this species belong to class C. They are bright reddish-white in 

 colour, and aggregated into a dense spike, being thus made so conspicuous that 

 insect-visits are very numerous. Cross-pollination is ensured by strong protandry, 

 and automatic self-pollination excluded. 



Hermann Mtiller states that nectar is secreted by eight fleshy, reddish glands 

 situated at the bases of the stamens, and stored at the bottom of the perianth-tube. 

 At first only the stamens project from the slightly open flower, the styles remaining 

 immature until the stamens have fallen, so that the stigmas then project about as far 

 beyond the perianth as the anthers did previously. 



Schulz says that in the Riesenge- 

 birge and the Alps, but rarely in the 

 lowlands, gynodioeciously, rarely gyno- 

 uionoeciously, distributed female flowers 

 occur (usually only up to 5 %), as well 

 as protandrous hermaphrodite ones. 

 In the Riesengebirge he also observed 

 flowers with shorter stamens in addition 

 to the form described above, in which 

 they project beyond the perianth. 



Kerner describes the spicate in- 

 florescence as consisting of small 

 cymes, made up of two, or rarely 

 three, flowers, of which one is long- 

 styled and hermaphrodite, and the 

 other male, with reduced style. In 



each of the cymes thus constituted the hermaphrodite flower opens first, anthesis 

 beginning at the bottom and proceeding upwards. Later on all the male flowers 

 open in the same way, and scatter their pollen on the stiU receptive stigmas of 

 adjacent hermaphrodite ones. 



Ludwig (D. bot. Monatsschr., Arnstadt, vi, 1888) states that small, pale, quite 

 immature buds are to be found on a young inflorescence together with the red 

 flower-buds, and these do not unfold until the anthesis of the primary flowers is quite 

 over. He distinguishes between the following stages : 



(i) Male stage of the primary flowers, four of the stamens ripening first and the 

 other four afterwards. 



(2) Female stage of the first generation. The anthers have dropped off" and 

 the stigmatic branches are divergent. The flowers close, and their colour becomes 

 brighter. Those of the second generation have not yet opened, but their pedicels 

 have elongated. 



(3) The stalks of the first generation, now setting fruits, are situated close to 

 the axis. Those of the second generation have elongated to such an extent that 

 they project far beyond those of the former. This is the male stage of the second, 

 generally paler generation. 



Fig. 351. Polygonum Bistorta, L. (after Herm. 

 Miiller). (i) Flower in the first (male) stage. (2) Do., 

 in the second (female) stage. 



