v.] VACCINIUM, PRIMULACE^. 125 



pollen derived from a previous visit ; and secondly, 

 in thrusting its proboscis up the bell, it inevitably 

 comes in contact with one of the anther processes, pr, 

 which then acts like a lever, and dislocates the whole 

 chain of anther cells, when a shower of pollen falls 

 from the open anther cells on to the head of the bee. 



Erica cinerea agrees very closely with E. tetralix. 

 In Erica (or Callund) vulgaris (the Common Heath), 

 on the contrary, where the flowers are, in their natural 

 position, more horizontal, the stamens and pistil 

 incline upwards, so that insects press their proboscis 

 under them, and in this manner the pollen is less 

 likely to be wasted, than if they were central as in 

 E. tetralix. In Erica vagans (the Cornish Heath), 

 E. carnea, and E. ciliata, the anthers have no ap- 

 pendages. 



In the allied genus Vaccinium there is an arrange- 

 ment similar to that in Erica, but the anther cells are 

 closed, not by touching one another, but by resting 

 against the style, so that the style itself closes the 

 openings until the anthers are disturbed by the 

 proboscis of the bee. V. uliginosum is much larger 

 than V. Myrtillus, and consequently more conspicuous ; 

 V. Myrtillus, on the other hand, has the compensating 

 advantage oi being richer in honey. 



The curious, brown-coloured, nearly leafless, Mono- 

 tropa (Yellow Birds-nest), differs very much from the 

 rest of the order. 



PRIMULACE^. 



This order is represented in Britain by eight genera : 

 Primula, Lysimachia, Trientalis, Glaux, Anagallis, 



