5° 



ANGIOSPERMAE—DICOTYLEDONES 



Hildebrand think that insects are driven away b)' the explosion of the stamens, and 

 transfer the pollen to other flowers. W. J. Beal says that the flowers are self-sterile. 



Visitors. — W. J. Beal observed the honey-bee, bringing about the explosion, 

 and effecting crossing. 



b. Tribe Pyroleae. 

 Flowers usually homogamous, with or without nectar. 



532. Pyrola L. 



Flowers generally white in colour ; nectar abundantly secreted in their bases, 

 or absent. Pollen-grains in tetrads. Anthers dehisce by pores. Flowers arranged 

 in radial racemes, or rarely solitary. 



1781. P. minor L. (Ricca, Atti Soc. ital. sc. nat., Milano, xiii, 1870 ; Warming, 

 Eot. Tids., Kjobenhavn, ii, 1877, pp. 122-4; Herm. Miiller, 'Alpenblumen,' pp. 376-7; 

 MacLeod, Bot.Jaarb. Dodonaea, Ghent, v, 1893, p. 452.) — Ricca describes the nectarless 

 flowers of this species as protandrous, but Warming, MacLeod and myself found them 

 to be homogamous. The five stigmatic lobes abundanily secrete a sticky fluid, which 

 in the absence of nectar appears to be licked by insect visitors before they search for 



Fig. 230. Pyrola rotimdifolia L. (after Henn. Miiller). A. Flower, seen immediately from the front 

 {X 3^). B. Pistil, seen from thi^ side. C- Stamens (X 7). gr^ style ; ov^ ovary ; i, calyx ; st, stigma. 



pollen, SO that their visits effect crossing. The anthers are erect in the bud, but 

 afterwards turn over, so that their basal pores, of which the margins are orange-red, 

 are directed downwards. Automatic self-pollination regularly takes place, should 

 insect-visits fail, by fall of pollen on the reflexed margin of the stigma. Warming 

 observed flowers of different size and breadth: — in some the petals come together to 

 form a globular bell with narrow aperture, and the stamens are relatively long ; in 

 others the corolla is more widely open, and the stamens are shorter. Warnstorf 

 describes the pollen-tetrads as four-sided, and 30-44 /x in diameter. 



Visitors. — Very few. The following were recorded by the observers, and for 

 the localities stated. — 



Herm. Miiller (Westphalia), a beetle (Dasytes flavipes i^.), constantly present in 

 large numbers, first visiting the stigma, then the stamens, and thus effecting crossing ; 



