142. Prickly lettuce, a compass plant

The lesson, step by step

1. When and where

   Comstock says this is a good lesson for late summer or September, in the field. Prickly lettuce grows in sunny waste places, roadsides and vacant lots. Young plants in full sun show the trick best. Its milky juice is sticky: wear gloves and wash hands afterward.

2. The leading thought

   Read it in parts. The key sentences:

   The young plants of wild lettuce prevent the sun from pumping them dry during drought, by turning the edges of their leaves toward the sun, and thus not exposing the leaf surface to its rays. The leaves thus lifted stand in one plane. They are usually directed north and south.

3. Look at the plant

   Where does the prickly lettuce grow? What sort of a stem has it? How are the leaves arranged on the stem?

   How do the leaves stand? Is their upper surface exposed to the rays of the sun? Which portion of the leaf is turned toward the sun?

4. Check with a compass

   Stand beside a plant with the compass. Which way do the flat sides of the leaves face? Which way do the edges point? Try several plants, including one in shade.

   How does the edgewise position of the leaf protect the plant during drought? Why does any plant wither during drought?

5. Prickles

   How are the leaves protected against grazing cattle?

   With gloves, turn a leaf over: there is a row of prickles along the midrib underneath.

6. Nature notebook

   Sketch a leaf showing its shape, its venation and its spines.

   Then draw the plant from above with a compass rose beside it and arrows for the leaf edges.