I04 THE NATURE-STUDY IDEA 



failed to grow was because of the *^ disappointment 

 of the sap." I laughed at the expression ; and yet 

 is it not as scientific as to say that the hairs exist 

 to keep the crowfoot warm or that the sumac 

 has poison to protect it from its enemies ? The 

 teacher may as well have said that Jimmie Brown 

 has freckles so that the sun will not tan 

 his skin ; and the statement would be hard to 

 disprove. 



The other'day a teacher asked me whether it is 

 not true that the cactus has spines in order to protect 

 it from browsing animals. I told her that I did not 

 know. As I was a stranger to her, she wondered 

 at my ignorance. She wanted to know why I did 

 not know. I told her that I had no good evidence 

 that an animal wanted to browse on a cactus. 

 Perhaps the cactus spines are older than browsing 

 animals. Perhaps there was some special condition 

 or reason in geologic time. Perhaps the spines 

 were in some way the incidental result of the 

 contraction of the plant body, which contraction 

 was associated with the necessity of reducing the 

 evaporating surface in an arid climate. Perhaps a 

 hundred things. She was surprised that I had to 

 go into geologic time to bury my ignorance. She 

 wanted cause and effect side by side and in the 

 present. Then she could see them. It is a bother 

 to look behind for causes. 



This is a typical case. This attitude toward nature 

 comes almost daily to the teacher ; in fact, it some- 

 times comes from the teacher. The mischief is 

 increased by many popular books on science, and 



