24 Elementary Plant Physiology. 



an unrolled frond which has not reached adult size. Mark off 

 divisions of one centimeter on the stips and on the lamina. 

 Osmunda or Asplenium will offer good material for this work. 

 Make measurements and determine the location of the zone of 

 maximum growth. 



10. Growth of a leaf with parallel veins. Mark off 

 intervals of one centimeter on a leaf of any of the early-bloom- 

 ing bulbous plants, such as Narcissus, Iris, or Gladiolus, and 

 make daily measurements to locate the zone of maximum 

 growth. Compare its position in such leaves with that of 

 dicotyledonous forms. What is the daily rate of growth? 



Make similar experiments with the leaves of Smilax glauca 

 or S. rotundifolia, in which the veins of fibrovascular tissue are 

 arranged in a slightly different manner. Is the method of en- 

 largement of a leaf correlated in any manner with the arrange- 

 ment of the veins? 



11. Rate of elongation of a leaf. Attach the tip of 

 a leaf of any plant used in the last experiment to the lever of a 

 mirror auxanometer, and determine the rate of growth during 

 an hour or two. Determine the rate during an hour early in 

 the morning and late in the afternoon. It would also be of 

 great interest to repeat the experiment as late as midnight. 

 Does the leaf elongate with the same rapidity at all hours of 

 the day? 



12. Growth of peduncles and scapes. Mark off 

 the scape of a young plant of Arisama, or any arum, into in- 

 tervals as above, and measure from day to day to ascertain 

 region of greatest growth and also daily rate of elongation. 

 Repeat with peduncles of tulip or any convenient plant. 



Attach the tip of a peduncle or scape to the mirror auxanom- 

 eter, and note the rate of growth during an hour early in the 

 morning, at midday, late in the afternoon, and late at night. 

 What variations are found ? 



13. Growth of petioles. Mark the petioles of young 



