A MANUAL OF BOTANY 41 



10. Place vigorous plants of various kinds in a window, 

 and allow them to remain for a few days. Turn each half 

 around and determine the varying rapidity of the response 

 of the leaves to the light. Seek for any explanation. 



11. Place a number of sprouting salsify, carrots, spinach 

 or other vegetables Jlat in a tray. Keep for 24 hours. 

 What direction have the youugeM leaves assumed? Split a 

 sprouting onion in halves. Place on the table with cut sur- 

 faces up. What happens to the sprouts ? 



12. As in 4, but place the whole plant in an inverted glass 

 bell jar of great height (16 in. or more) filled with water. 

 Place in bright sunlight. Observe gas ; collect and test for 

 oxygen. 



13. As in 1, but grow in the light until vigorous. Place 

 in closet at close of day, bring out the next morning, and 

 lower a taper to the bottom. What happens ? P)reathe 

 repeatedly into a similar deep glass and test as before. 

 Compare the two. 



14. Take fresh leaves of fern, lettuce, plantain, beet, 

 maple, mullein, sunflower, water lily, corn, carrot, and oniou. 



Allow each to remain on the table in dry room for one 

 hour or until well wilted. Kecord varying time. 



Now plunge each into cold water and let it remain for 

 some time. What amount of revived freshness does each 

 show ? AVhat caused the wilting and how did the cold bath 

 r«?store ? 



8. EcoL()(;i('AL Study ov Leaves 



Field work. Throughout the season, from early spring to 

 fall, find out and observe carefully as many rosette forms 

 of leaves as possible. Rosettes found in early spring, es- 

 pecially, should be noticed, with the locality in which each 

 grows. What do you infer, by studying each, as to the 

 plants' life duration ? How did they survive tlie cold 

 weather? What })roportion of the plants having rosettes 



