MONOCOTYLEDONS. 



295 



downwards and pointing forwards, and the thick end of a 

 pollinium touches the stigma of the next flower visited (Fig. 

 115 B, c), and the sticky stigma drags off some of the packets 

 of pollen. 



The pollinia remain fixed on the bee's head, as the sticky 

 disc soon hardens, so that a single pollinium may be carried 

 about and pollinate several flowers before all the pollen is 

 pulled off by the stigmas. One often sees a bee, which has 

 been visiting Orchids, carrying a dozen pollinia stuck on 

 its head, base of tongue, and thorax. 



COLUMN .._ 



STIGMA-. 



SPUR 



BRACT 



Fig. 115. Pollination of Orchid by a Bee. 



At C the polliuia have bent forward and will touch the stigma of the next flower 



visited. 



Poke a pointed pencil into the spur of the labellum (to 

 imitate the action of a bee thrusting in its tongue to scrape 

 the honeyed walls of the spur). Notice the two club-shaped 

 masses, of pollen which are withdrawn from their pockets and 

 remain attached to the pencil by the sticky mass at the base 

 of their stalks. What change in position do the pollinia 

 undergo after being removed, and how does this help in 

 bringing about cross-pollination ? 



Where is the ovary ? Examine the apparent stalk of the 

 flower, opening it up with a pin or the point of a knife. 

 Note the three ovule-bearing strips (placentas) on the inner 



