312 BRITISH FLOWERING PLANTS chap. 



LiMOSELLA 



A small floating annual. 



L. aquatica. — According to Kerner, if the small pink 

 flowers are submerged they become cleistogamous. 



Digitalis 

 (Foxglove, i.e. Folksglove or Fairy's-glove) 



Protandrous humble bee flowers, with nectar secreted 

 by a ring surrounding the base of the ovary. 



D. purpurea. — Beautiful purple flowers in, as Bentham 

 well says, " a long stately raceme." The flowers hang 

 downwards, and are thus protected against rain. The 

 posterior sepal is small, a step towards its complete 

 suppression in the next genus (Veronica). The in- 

 terior of the corolla is lined with hairs, which Kirchner 

 regards as intended to prevent the entrance of small 

 creeping insects. Knuth doubts this, and suggests that 

 they perhaps rather serve to give a foothold to the 

 friendly visitors. May they not be useful for both pur- 

 poses ? The size of the flower is well adapted to that 

 of humble bees. The anthers and stigma are not spread 

 out round the circumference of the corolla, but are 

 arranged together on the upper side. The fifth stigma, 

 which was fully developed and useful in Verbascum, 

 and has lost its anther in some species of Scrophularia, 

 in this and the following genera of the family has en- 

 tirely disappeared. The pistil lies along the centre of 

 the upper lip between the anthers, which are in two pairs, 

 one in front of the other, so that they must be touched 

 by the back of an insect entering the flower. The 

 anthers of the two longer stamens open first, then those 

 of the shorter ones, after which the two stigma lobes 

 open. If humble bees are abundant the pollen may be 

 removed before the stigmas are ripe ; if any pollen 

 remains the flower might easily fertilise itself. Accord- 

 ing to Darwin, however, it is self-sterile. The anthers 

 (Figs. 199-201) are at first horizontal, but as they ripen 



