FLORAL MECHANISMS 



105 



Dr. Henry Smith .Williams in his Life and Work 

 of Biirhank tells us that the peas and beans 

 of the vegetable garden keep all their pollen at 

 home and are self-fertilising. Ho\\e\'er, the flow- 

 ering sweet pea, the pink locust and the lupin bear 

 evidence in their flowers that they invite the bees 

 to enter. The colour and fragrance alone show 

 this intention, and the mechanism is perfectly com- 

 prehensible. Glanc- 

 ing at the sketch, 

 we see that the sta- 

 mens and pistil are 

 protected from rain 

 and marauders in 

 the boat - shaped 

 lower petal, which 

 forms a handy landing-stage, but one which will 

 give way a little under the weight of a bee. Now, 

 it happens that the stamens and pistils are so stiff 

 that, as the boat sinks, they come up from the 

 main hatch and touch the under side of the bee. 

 The pistil, being the longer, comes up first and 

 gets a touch of pollen if any has been brought 

 from afar; the stamens then follow and give up 

 their store. 



Then the bee, having quenched his thirst, flies 

 away; the boat rises into place again, and the 



SWEET PEA 



