INSECTS AND FLOWERS 197 



turn their backs to the latter. As soon as they 

 touch the upper antenna of the male flower, the 

 pollen-mass, with its disk and gland, is fixed on 

 their back, and they are often seen flying about 

 with this peculiar-looking ornament on them. 

 I have never seen it attached except to the very 

 middle of the thorax. When the bee walks 

 about, the pollen-mass lies flat on the back and 

 wings; but when the insect enters a female 

 flower, always with the labellum turned up- 

 wards, the pollinium, which is hinged to the 

 gland by elastic tissue, falls back by its own 

 weight and rests on the anterior face of the 

 column. When the insect returns backwards 

 from the flower, the pollinia are caught by the 

 upper margin of the stigmatic cavity, which 

 projects a little beyond the face of the column ; 

 and if the gland be then detached from the back 

 of the insect, or the tissues which connect the 

 pollinia with the caudicle, or this with the gland, 

 break, fecundation takes place." 



The flower of the common Nasturtium 

 (Tropaeolum major) of our gardens, from the 

 time of its first opening until its petals droop, 

 passes through three distinct stages. The 

 brilliant colour of the flower is in itself suffici- 

 ently striking to attract the visits of insects, 

 but in addition we find that there is a sip of 

 nectar awaiting these winged visitors in the 

 long tapering spur. When the flower first 

 opens, the anthers are unripe, and the pistil is 

 short and immature; very soon after the opening 

 of the flower, however, one of the anthers 

 matures, opens, and turns up in such a way as 



