CHAPTER XVII 



SOME FLORAL ADVERTISEMENTS 



The more one studies floral structures the more 

 obvious does it become how perfect is the special- 

 isation of each for the visits of the particular 

 insects that best convey their pollen from bloom 

 to bloom. There are reasons for even the most 

 insignificant detail in their mechanism ; every 

 allurement is offered to attract their special insect 

 guests. Look at the tall racemes of the Foxglove 

 {Digitalis purpurea) shown in Fig. no (Plate 79) 

 Each axis stands from two to four feet in height, 

 and, arranged along its length, its drooping bell- 

 shaped flowers open from below upwards. The 

 foxglove is never so comfortable as when backed 

 closely by the edge of a wood, or even the road- 

 side hedge ; there its tall flower stems are 

 sheltered from the wind and run little risk of 

 getting broken. That protection, however, pre- 

 sents a problem ; in such a situation one side of 

 the plant is necessarily shaded. The humble-bees, 

 for which alone the foxglove flowers are designed, 

 love the sunlight ; there lies the difficulty. Thus 

 the foxglove's flower stem is what the botanist 

 terms a simple, one-sided raceme. Or, to put 

 the point more suggestively, the foxglove turns 

 all its bell-shaped flowers from the shady hedge- 



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