Lesson CXXVIII

The Evening Primrose

Leading thought—Some flowers have developed the habit of relying on the night-flying insects for carrying their pollen. The evening primrose is one of these; its flowers open in the evening and their pale yellow color makes them noticeable objects in the twilight, and even in the dark.

Method—The form of the evening primrose may be studied from plants brought to the schoolroom; but its special interest lies in the way its petals expand in the evening, so the study should be continued by the pupils individually in the field. This is one of the plants which is an especially fit subject for the summer note-book; but since it blossoms very late and the plants are available even in October, it is also a convenient plant to study during the school year. The garden species is well adapted for this lesson.

Observations—1. Look at the plant as a whole. How tall is it? Is the stem stiff and straight? Where do you find it growing? Does it grow in the woods?

2. Are the leaves near the base the same shape as those at the top of the plant? What is their shape? Are the edges toothed? What is there peculiar about the veins? How do the leaves join the stem? How do the leaves look which are at the base of the flower stem? Those at the base of the buds?

3. Where on the plant do the flowers grow? Which flowers blossom first, those above or below? Take a bud nearly ready to open; what is there peculiar in the appearance of the bud stem? What is the general shape of the bud? Describe the sepals. Look at their tips carefully, and see how they hold together. Cut a bud across and see how the petals are folded within it.

4. Take an open flower; where are the sepals now? Describe the open petals, their shape and color.

5. How many stamens are there? How are they placed? What is the shape of the anthers? How does the pollen look?

6. What is the shape and the position of the stigma in the freshly opened flower? Later? Open the flower-tube and find how far down the style extends. Where is the ovary? How does the ovary look on the outside? Taste the opened tube; can you detect the nectar? What sort of a tongue must an insect have to reach this nectar? How do the fading flowers look and act?

7. Describe the seed-pod. Cut it across, and see how many compartments there are within it. How are the seeds arranged in it? How do the pods open and how are the seeds scattered?

8. Watch the flower of the evening primrose open, and describe the process carefully. At what hour did it open? What was the movement of the petals? Can you see how they unfold in relation one to another? How do they get free from the sepals? How many minutes is required for the whole process of the opening of the flower? How many flowers on a plant expand during the same evening? Look at the open blossoms in the dark; can you see them? How do they look? What insects do you find visiting these flowers?

9. How long does the primrose blossom remain open? How do the young plants of the evening primrose pass the winter?

Supplementary reading—Blossom Hosts and Insect Guests, Gibson.