172 ELEMENTS 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. 
Irregular 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. 
Fie. 128. A Beetle on the 
Flower of the Twayblade. 
(Enlarged three times.) 
1 See P. Knuth, Handbuch der Bliithenbiologie. 
