158 DICOTYLEDONS 



{Antirrhinum) and the Toadflax (Linarid), with irregular 



flowers, have four stamens, alternating with petals, and in 



addition they may have a fifth stamen, which is smaller, and 



^..^ a^ . is median posterior 



# y Z' \ f % f"' \ in position (fig. 196) ; 



* i \ j \ ] \ y in the Figwort {Scro- 



~ — • ^—* ^—^ ■-. . phularid) the same 



195 196 197 198 arrangement is found, 



Figs. 195-198.— Diagrams of the androscium of but the median pOS- 



Scrophulariaceae. ... . • . 



tenor stamen exists 

 in the form of a scale-like staminode. In the Foxglove and 

 many other types the posterior stamen has completely dis- 

 appeared, so -that only four stamens are present (fig. 197). 

 Finally, in the Speedwell ( Veronica) the two anterior stamens 

 have also vanished, so that the flower possesses only two lateral 

 stamens (fig. 198). The flower of the Speedwell is not two- 

 lipped ; it has a very short corolla-tube, and the two 

 posterior petals are so closely united as to look like a single 

 petal. 



THE SHAPES OF SCROPHULARIACEOUS FLOWERS AND 

 THE INSECTS POLLINATING THEM. 



In the Scrophulariacese we can see that the varied forms of 

 flowers pollinated by insects are to be explained by observing 

 the insects which pollinate them. The Speedwell (Veronica 

 chamcedrys), with open small flowers, having a very short 

 corolla-tube and easily accessible honey, is especially cross- 

 pollinated by certain flies — hover-flies : it is a Hover-fly-flower. 

 The Figwort {Scrophularid), with short, wide chocolate-coloured 

 flowers, and easily visible honey, is particularly cross-pollinated 

 by wasps : it is a Wasp-flower. The Foxglove, Snapdragon, 

 and Toadflax possess flowers with long corolla-tubes and 

 deeply-placed honey ; the visiting insect creeps bodily into the 

 tube, and its body must fit the flower if cross-pollination is to 

 be ensured; thus large-bodied bees are the sole cross-pollin- 

 ating agents : they are Bee-flowers, especially Large-bee- 

 flowers. The Snapdragon - flower is closed, so that only a 

 strong insect can push its way in and reach the honey; the 

 pollen and honey are consequently well protected against rain 

 and marauding insects. 



