DROSERACEAE 431 



XXXVII. ORDER DROSERACEAE DC. 

 285. Drosera L. 



Most of the flowers, according to my observations in Schleswig-Holstein, are 

 cleistogamous (cf. Vol. I, p. 54). It is only in very favourable continuously sunny 

 weather that the small white blossoms open, and anthesis is confined to a single 

 morning. Hansgirg describes the species of this genus as pseudo-cleistogamous. 



Kerner states that nectar is secreted by the yellow claws of the petals in the 

 chasmogamous flowers. After the brief anthesis the flowers close again, and the six 

 stigmatic lobes of the style curve in such a way that their receptive papillae touch 

 the pollen-covered anthers. This self-pollination is effective. 



1017. D. rotundifolia L. (Kirchner, 'Flora v. Stuttgart/ p. 322 ; Knuth, 'Bl. 

 u. Insekt. a. d. nordfr. Ins.,' p. 34.) The white flowers of this species open but 

 rarely, and are only 3 mm. in diameter, so that there can scarcely be any question of 

 insect-visits. The five anthers dehisce when the flower opens, and are at the 

 same level as the simultaneously matured stigmas, from which they are only 

 | mm. distant, so that automatic self-pollination can easily take place, especially 

 when the flower closes towards the end of anthesis. Either cross- or self-pollination 

 may be effected by insect-visits to the open flowers. In those which remain closed 

 the stamens and carpels touch one another when mature. Such cleistogamous 

 flowers produce abundant seed. 



Visitors. In Dumfriesshire, several Muscids were observed (Scott-Elliot, ' Flora 

 of Dumfriesshire,' p. 73). 



1018. D. intermedia Hayne. (Knuth, 'Bl. u. Insekt. a. d. nordfr. Ins.,' p. 34.) 

 The flower mechanism of this species agrees with that of D. rotundifolia. Cleisto- 

 gamous flowers are even more frequent. 



1019. D. anglica Huds. (Warnstorf, Verh. bot. Ver., Berlin, xxxviii, 1896.) 

 The flowers of this species are mostly pseudo-cleistogamous, many of them opening 

 about mid-day, but soon closing again. The stigmatic branches and the anthers 

 mature simultaneously before anthesis ; the latter are very small, and borne upon 

 thick filaments. The pollen-grains are golden-yellow in colour, densely covered 

 with spinous tubercles, and aggregated into 3-4 celled pollinia. 



286. Aldrovanda Mont. 

 The flowers are mostly cleistogamous, according to Bentham and Hooker. 



1020. A. vesiculosa L. (Korzchinsky, ' Zur Kenntnis der Aldrovanda vesicu- 

 losa.') Korzchinsky states that in the flowers of this species each anther contains at 

 most thirty-five pollen-grains. The anthers get bound to the stigma by pollen-tubes, 

 but most of the ovules remain unfertilized, even though they swell up with the ovary. 



XXXVIII. ORDER BRUNIACEAE R. Br. 

 The flowers are aggregated into small capitula, and their mechanism resembles 

 that of the Compositae. According to Delpino (' Ult. oss.,' p. 98) and Hildebrand 

 (Bot. Ztg., Leipzig, xxviii, 1870, p. 636), the end of the style bears a glabrous bilobed 

 collecting-cup, which grows through the anther-tube and thus takes up the pollen. 

 The stigmatic surface appears upon it later. 



