POLLINATION OF ORCHIDS. 797 



fast there ; on again withdrawing they remain fixed there, wholly or partly torn away 

 from the pencil. In virtue of the form and position of the parts of the flower, 

 then, an insect which settles on the anterior portion of the labellum can creep 

 down into the base of the nectary without touching the rostellum ; on creeping 

 out after sucking the nectar it strikes against it and takes away the pollinia with 

 it. On creeping into a second flower these pollinia come on to the viscid stigmatic 

 surface and there remain fixed. In some other Orchids the relations are far more 

 complicated. 



(3) In flowers which are pollinated by insects, the mature pollen must often 

 remain lying in the already dehisced anthers for some time before it is removed ; 

 during this period it must neither be dispersed by the wind nor moistened by rain or 

 dew. Numerous and very various adaptations therefore exist for the protection of the 

 pollen, further details as to which are given by Kerner in his work ' Die Schutzmittel 

 des Pollens,' (Innsbruck, 1873). 



