Wild-Flower Study 571 



It also has another "anchor to the windward." A plantso full'of juice 

 would prove attractive food for cattle when pastures are dry. The leaves 

 of this lettuce escape, because each has a row of very sharp spines on the 

 lower side of the midrib. At first we might wonder why they are thus 

 placed; but if we watch a grazing animal, as a cow, reach out her tongue 

 to pull the herbage into her mouth, we see that these spines are placed 

 where they will do the most efficient work. The teasel has the same 

 clever way of warning off meddlesome tongues. The prickly lettuce also 

 has spines on its stem, and the leaves are toothed with spines at their 

 points. 



LESSON CXLII 

 PRICKLY LETTUCE 



Leading thought The sunshine sets the machinery in the leaf-factories 

 going, and incidentally pumps up water from the soil, which pours out 

 into the air from the leaves ; but if the soil is dry the pump works just the 

 same, and the plant thus robbed of its water soon withers and dies. The 

 young plants of wild lettuce prevent the sun from pumping them dry dur- 

 ing 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. The lettuce also 

 has spines to protect it from grazing animals. 



Method The lettuce should be studied in the field, and is a good sub- 

 ject for a lesson in late summer or September. This lesson should supple- 

 ment the one on transpiration. The young plants show this arrangement 

 of the leaves best. The flowers may be studied by the outline given in 

 Lesson CXXXV. 



Observations i . Where does the prickly lettuce grow? What sort of 

 a stem has it ? How are the leaves arranged on the stem ? 



2. If the leaves stood straight out from the stem, what would be the 

 shape of the plant? 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 ? 



3. If the leaves turn sideways and stand in one plane, do they stand 

 north and south or east and west. How does the edgewise position of the 

 leaf protect the plant during drought ? Why does any plant wither dur- 

 ing drought? If the leaves of the lettuce should extend east and west 

 instead of north and south, would they get more sun? (See lesson on the 

 Sun.) 



4. What is the shape of the lettuce leaf? How does it clasp the stalk? 

 How is the base shaped so that the leaf can turn without tearing its 

 edges? Sketch a leaf thus turned fully, showing how it is done. Does 

 the leaf turn toward the stem or away from it ? 



5. How are the leaves protected against grazing cattle? How does 

 the cow use her tongue to help bring herbage to her mouth ? How are the 

 prickly spines placed on the lettuce leaf, to make the cow's tongue un- 

 comfortable? Sketch a leaf showing its shape, its venation and its 

 spines. 



