150 On the Campus 



less interference with the proper foliage display. The 

 leaves of the prairie compass plant at mid-day stand 

 edgewise to the south ; that is, avoid maximum illumina- 

 tion; and many plants, especially in dry regions, set 

 their leaves slantwise to the sun and so control the 

 amount of illumination. More remarkably still, many 

 plants well deserve the name "sensitive." Shelley, as 

 we all know, made the "sensitive plant" famous. 



"A sensitive plant in a garden grew, 

 And the young winds fed it with silver dew, 

 And it opened its fan-like leaves to the light, 

 And closed them beneath the kisses of night." 



The sensitive plant is indeed a marvel ; but is the won- 

 der lessened when we reflect that hundreds of other 

 plants respond to external stimuli in much the same 

 fashion? The common clovers and sorrels of the fields 

 "change their position as the light of day grows and 

 wanes ; they are expanded during the day and fold down- 

 wards in the evening. ' ' The common locust is notorious 

 in such response. In 1869 when the sun underwent total 

 eclipse the leaves of the locust trees retired with the 

 turkeys that clambered to their branches. The cour- 

 teous mimosas of the tropics bow as the traveler passes 

 amid their shining ranks, and remain drooping in kow- 

 tow for some minutes after he has passed. These move- 

 ments are primarily, no doubt, responses to the varying 

 amount of light and have only later become amenable 

 to the ruder forms of irritation. Your gentle stroking 

 of the sensitive plant is rudeness itself compared with 

 those finer thrills long since resultant from the onset 

 of the light. Yet again ; the light is not all. Plants are 



