172 



ESSENTIALS OF BOTANY 



204. Nectar Guides. — In a large number of cases the 

 petals of flowers show decided stripes or rows of spots of 

 a color different from that of most of the petal. These 

 commonly lead toward the nectaries, and it is possible 

 that such markings point out to insect visitors the way to 

 the nectaries. Following this course, the insect not only 

 secures the nectar which he seeks, but probably leaves 

 pollen on the stigma and becomes dusted with new pollen, 

 which he carries to another flower. 

 205. Facilities for Insect Visits. 

 — Regular polypetalous flowers 

 have no special adaptations to make 

 them singly accessible to insects, 

 but they lie open to all comers. 

 Bisexual flowers probably always 

 are more or less adapted to partic- 

 ular insect (or other) visitors. The 

 adaptations are extremely numer- 

 ous; here only a very few of the 

 simpler ones will be pointed out.^ 

 Where there is a drooping lower 

 petal (or, in the case of a gamopetalous corolla, a lower 

 lip), this serves as a perch upon which flying insects may 

 alight and stand while they explore the flower, as the 

 beetle is doing in Fig. 128. In Fig. 129 one bumblebee 

 stands with her legs partially encircling the lower lip of 

 the dead-nettle flower, while another perches on the sort 

 of grating made by the stamens of the horse-chestnut 

 flower. The honey-bee entering the violet clings to the 

 beautifully bearded portion of the two lateral petals while 

 it sucks the nectar from the spur beneath. 



1 See Knuth-Davis' Handbook of Flower Pollination. 



Pig. 128. A Beetle on the 

 Flower of the Twayblade. 

 (Enlarged three times.) 



