130 ERICACEAE. [CHAP. 



separate, so that by the time the pollen is all removed 

 the flower is in the state shown in Fig. 92, and it 

 is evident that any bee which may have visited a 

 younger flower, and dusted its under side with pollen, 

 can hardly fail to deposit some of it on the stigmatic 

 surfaces thus extended for its reception. 



It had been supposed that the hanging position of 

 Campanula and other bell-shaped flowers had reference 

 to the position of the stamens and pistil, so that the 

 pollen might fall from the former on to the latter. 

 Sprengel, however, pointed out that the real advan- 

 tage to the flower consisted in the fact that the honey 

 is thus protected against rain. If the pollen fell on 

 to the stigma, it is indeed obvious that the stigmatic 

 surface should be turned upwards, whereas it is at the 

 end of the pistil, and is consequently turned down- 

 wards, showing that the pollen comes from below and 

 not from above. 



The other British genera of Campanulaceae are 

 Lobelia, Jasione, and Phyteuma. 



ERICACEAE. 



This order contains ten British genera. 



Erica tetralix (the Cross-leaved Heath) has been 

 well described by Dr. Ogle (Popular Science Review, 

 April 1870). The flower is in the form of a bell 

 (Fig. 93), which hangs with its mouth downwards, 

 and is almost closed by the pistil, and stigma (st\ 

 which represents the clapper. The stamens are eight 

 in number, and each terminates in two cells, which 

 diverge slightly, and have at their lower end an oval 



