ERICACEAE 49 



characters. The pollen-grains are smaller, and their walls often shrivelled (Abromeit, 

 ' Bot. Ergeb. von Drygalski's Gronlandsexped./ pp. 51-8). The stamens are usually 

 ten in number, and project a little beyond the style. Some of the brownish or 

 yellowish anthers appear to be reduced. 



530. Rhodora L. 



Flowers homogamous, with concealed nectar ; the stigma is at first covered as 

 with a cap by the middle lobe of the upper lip. 



1779. R. canadensis L. (= Rhododendron Rhodora/. F. Gmel). (Hilde- 

 brand, Flora, Marburg, xxxix, 1881.) Hildebrand gives the following account of this 

 species. 



The corolla possesses two lower lobes separate almost to the base, and a three- 

 lobed upper lip, the central division of which covers the opening of the flower like 

 a cap, holding fast the elongating style so that it is bent sharply downwards at its 

 centre. There are ten stamens, of which the upper ones are shorter with tips bent 

 downwards, while the longer lower stamens are bent upwards. The anthers are so 

 placed that their apical pores surround the opening of the flower, so that an insect 

 visitor must dust itself with the pollen by which these are covered. The continued 

 elongation of the style causes it to spring out of the cap at a later stage, and it now 

 projects beyond the anthers so that an insect visiting the flower must first touch it, 

 securing cross-pollination if already dusted in another flower. Autogamy is not 

 absolutely excluded, but as visitors have usually removed all the pollen before the 

 stigma emerges, it is generally impossible. 



531. Kalmia L. 



The anthers are situated in pouches of the corolla, and the elasticity of the 

 filaments causes them to spring out when insects visit the flower. Drude gives the 

 following description of the mechanism (in Engler and Prantl, * D. nat. Pflanzenfam.,' 

 IV, I, p. 25). 



The anthers are enclosed in pits of the wheel-shaped corolla, the margins of 

 which prevent them springing out prematurely, though the filaments are strongly 

 bent inwards and in a state of elastic tension. In warm sunshine the elasticity of the 

 filaments increases, and they perhaps become shorter, so that the slightest touch 

 causes them to spring out and scatter a cloud of pollen from their dehisced anthers. 

 Drude's observations were made in the Dresden Botanic Garden, where he never saw 

 the liberation effected by insects, which curiously did not appear to visit the bright red 

 flowers. In favourable weather it took place spontaneously, and was followed in due 

 course by the formation of seeds. The pollen reaches the stigmas of neighbouring 

 flowers much more easily than that of the one in which it is produced, but autogamy 

 is not excluded. 



1780. K. glauca Ait. ( = K. polifolia Wangen.). (Sprengel, *Entd. Geh.,' 

 pp. 238-40; Delpino, 'Ult. oss.,' p. 169; Hildebrand, Bot. Ztg., Leipzig, xxviii, 

 1870, p. 669; W. J. Beal, Amer. Nat., Boston (Mass.), i, 1868.) Sprengel supposed 

 the flower mechanism of this species to be adapted to self-pollination. Delpino and 



DAVIS. Ill 



