114 SOUTH AFRICAN BOTANY 
species of Abutilon and Passiflora. Closely allied to this 
is the phenomenon of pollen-prepotency. If the stigma 
of a plant A be pollinated from the stamens of A, and 
from the stamens of another flower B, the ovules will 
be fertilized by the pollen of B and not of A, even though 
the pollen from A was there first. 
(e) Special devices.—Many flowers have special devices 
for ensuring cross-pollination, which do not come under 
A flap closing 
2 stigma 
-pertanth tube 
-- Ovary 
Fig. 64.—Iris Flower with Petals Removed. 
any of the above headings. The Inis (fig. 64) has petal- 
oid styles under which are the three stamens with their 
extrorse anthers. Just above the stamen is a little flap, 
the upper surface of which is the stigma. The honey 
is at the bottom of the perianth tube, and the three 
inner perianth lobes are striped so as to act as honey 
guides. Insects entering the flower to get the honey 
first deposit the pollen brought from another flower on 
the stigma; then as they go farther in they get a further 
supply of pollen from the stamens, and when they come 
out they close the stigma flap, thus preventing self- 
