LEAVES 143 



maple, grape, etc., as to size, surface, outline, color, shape, 

 and any other differences. Which are broadest in propor- 

 tion to their width? Which are rough, smooth, glossy, 

 downy, etc.? 



Make collections of leaves, ' press them, mount them on 

 cards, and label them for future reference. 



Petiole or Leafstalk. Compare leaves of poplar, cherry, 

 beech, burdock, tiger lily, tropaeolum, sycamore, pitcher 

 plant, water hyacinth, etc., as to length, shape, size, color, 

 appendages, etc. Why are the leafstalks of upper leaves 

 of maple and horse-chestnut shorter than those of the leaves 

 farther down the stem? Compare leafstalks as regards 

 special functions. Of what use is the caplike base of the 

 sycamore (platanus), the inflated petiole of the pitcher 

 plant, the swollen spongy petiole of the water hyacinth, 

 the grooved petiole of the burdock and celery, and the ten- 

 dril-like character of the tropaeolum and clematis? 



Stipules. Procure leaves of pansy, locust, sweet pea, 

 smilax, apple, rubber plant, tulip tree, red clover, rose bush, 

 etc. Be careful to secure the entire leaf. Stipules often 

 are so firmly adherent to the stem as to remain attached 

 when the leafstalk is broken away. Some plants also shed 

 the stipules when the leaf unrolls and are supposed to have 

 none when in reality these stipules have already been shed 

 (caducous or evanescent). Notice the modification of stip- 

 ules. Which help to climb? Which act as a means of 

 defense? Which are leaflike? Which seem to be solely 

 for protection of the bud? 



Make sketches showing all forms of stipules seen. Which 

 ones fall off at the opening of the bud ? Which ones remain 

 permanently attached to the stem? Study the stem of a 

 rubber plant; sketch the terminal bud with its interesting 



