TAKING UP OF POLLEN BY INSECTS. 



247 



Instances are very common in which insects in seeking honey brush the upper 

 parts of their bodies against the anthers, thus covering their backs with pollen. 

 Humble-bees, when they visit Iris flowers (fig. 265), settle on the hairy ridges of 

 the outer deflexed perianth-segments as the most convenient alighting-places, and 

 thence proceed to the honey-containing canals of the perianth-tube. They thus pass 

 under one of the petaloid stigmas, and at the same time under the corresponding 

 stamen, which is so placed and curved as to exactly fit the dorsal surface of the 

 humble-bee. The pollen is thus brushed off on to the insect's back. Similarly, bees 

 entering the gaping flowers of Gladiolus, of the Dead Nettle (Lamium) and other 

 Labiates rub their backs against the anthers, which are concealed close underneath 

 the upper lips, and carry away pollen on that part of their bodies only. The same 

 holds good in the case of the humble-bees which slip into the large bells of Gloxinia, 

 clamber up to the honey in Foxglove flowers (Digitalis), or venture into the jaws of 



Fig. 266. — Longitudinal section through a flower of the Evening Primrose ((Enotkera biennw). 



the Snapdragon or Toad-flax {Antirrhinum, Linaria). In the flowers of Linaria 

 two pairs of large anthers are situated close under the arch of the upper lip, and 

 the pollen discharged by them is in the form of two round balls, which are both 

 detached at once from the fissures in the anthers upon the occasion of an insect's 

 visit, and are carried away to other flowers on the back of the intruder. 



The laterally-directed flowers of the Evening Primrose (CEnothera; see fig. 266) 

 are visited by moths which insert their probosces into the long floral tubes as they 

 flutter about in front of the flowers. In so doing, the moths brush their heads 

 against the anthers surrounding the entrance to the flower-tubes, and cover them 

 with pollen. The head is also the part aff'ected in the case of the Sun-birds (Gin- 

 nyridcB) which take the rich brown honey from the lower, bowl-shaped sepal of 

 Melianthus flowers (see fig. 258 ^^, p. 227), and in the process bring their heads into 

 contact with the anthers above it. 



The adaptation of flowers with a view to ensuring that insects seeking their 

 honey shall brush ofi" the pollen with some part of their bodies, whether back, 

 belly, shoulders; head, or at least the proboscis, is of so manifold a character that 

 it is impossible, having regard to the scope of the present work, to deal with all 

 the contrivances coming under this category. Only a few of the most striking 



