Answer:
A-There are two different types of primrose flowers: some have a pin-eyed stigma which rises above the pollen-bearing anthers, while in thrum-eyed flowers the stigma is enclosed by the anthers. Long-tongued insects like butterflies and bee-flies visit the flowers to reach the nectar at the base of the flower-tube.
B-An insect visiting a pin-eyed flower first collects pollen from the lower anthers on the middle of its proboscis, which it then transfers to the stigma in a thrum-eyed plant, which is positioned lower down the flower tube. It's an ingenious adaptation which ensures that primroses will be successfully cross-pollinated.
C-Many plants have ensured that cross-pollination takes place by deliberately keeping male and female flowers on the same plant out of sync. In this corn plant, the pollen is ripe long before the stigmas are receptive; therefore, the only way the ovules can be fertilized is by the pollen from another corn plant.
D- When they visit a thrum-eyed plant, the pollen from the anthers, which are near the top of the tube at the entrance, attaches to the top of the insect’s proboscis. When it visits a pin-eyed flower and probes deeply for nectar, the pollen is in a perfect position to be transferred to the higher stigma of this flower. An insect visiting a pin-eyed flower first collects pollen from the lower anthers on the middle of its proboscis, which it then transfers to the stigma in a thrum-eyed plant, which is positioned lower down the flower tube. It’s an ingenious adaptation which ensures that primroses will be successfully cross-pollinated.
Explanation:
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