SCROPHULARINEAE 



i8i 



2IOI. D. purpurea L. (Sprengel, 'Entd. Geh.,' p. 325; Ogle, Pop. Sci. Rev., 

 London, ix, 1870, p. 49 ; Herm. Miiller, * Fertilisation/ pp. 437-8 ; Ludwig, Kosmos, 

 Stuttgart, xvii, 1885, p. 107; Kirchner, "Flora v. Stuttgart,' p. 585; Knuth, 

 ' Blutenbiol. Beob. in Thiiringen,' ' Blutenbesucher,' II, ' Bliitenbiol. Beob. a. d. Ins. 

 Rugen'; ' Bloemenbiol. Bijdragen.') The large red flowers of this species are 

 aggregated into very conspicuous unilateral racemes. Their form is that of an 

 elongated, somewhat flattened cylinder, obliquely truncated, and slanting down- 

 wards: 4^5^ cm. long and i-5-i-7 cm. broad. {Cf. Fig. 290.) The position 

 and form of the corolla protect the internal parts of the flower from rain. The 

 inner side of the corolla on its somewhat produced lower lip is provided with 

 nectar-guides in the form of dark-purple blotches with white margins. This 

 region is beset with hairs 5 mm. long, which serve, according to Kirchner, to 

 prevent the smaller useless insects from getting at the nectar. It seems to me, 

 however, that they are so loosely arranged and so limited in extent, that they 

 are not able to prevent such insects from 

 creeping into the flowers. My opinion is 1 

 that these hairs give insect-visitors a firm 

 grip. 



Nectar is secreted by an annular swell- 

 ing below the ovary, and stored in the base 

 of the corolla-tube. The dimensions of the 

 bell correspond to those of humble-bees, 

 and as a matter of fact it is these insects 

 only which seek out the nectar of the fox- 

 glove and eff"ect pollination in doing so. 



The style and stamens lie against the 

 upper side of the corolla on the way to the 

 nectar, so that a humble-bee creeping right 

 into the flower and probing for nectar must 

 touch the anthers and stigma with its dor- 

 sal surface. The anthers of the two long stamens first dehisce, then those of the 

 short ones, and finally the stigmatic lobes diverge. When the visits of humble-bees 

 are numerous, all the pollen is removed from the anthers before the stigma is 

 mature, so that cross-pollination is inevitable. Should there be no such visits, the 

 anthers are covered with pollen when the stigmatic lobes diverge ; hence automatic 

 self-pollination is possible. This is apparently effective, for in continuous rainy 

 weather almost all the flowers set fruits. Darwin, however, describes the flowers as 

 self-sterile. Kerner says that the anthesis of an individual flower lasts for six days. 



Besides protandrous hermaphrodite flowers, Ludwig also observed small- 

 flowfered female stocks, which make up about i % of the whole in the neighbourhood 

 of Kleinschmalkalden. These female flowers are not only smaller than hermaphrodite 

 ones, but also less strongly zygomorphous. Their stamens are reduced, and the 

 anthers contain shrivelled pollen-grains. All the vegetative parts of the female 

 stocks are also dwarfed. 



Fig. 290. Digitalis purpurea, L. (after Plateau). 

 Flower, natural size. 



Visitors. 

 stated. 



-The following were recorded by the observers, and for the localities 



