342 Plant Physiology 



Mark off also convenient (about 2 mm.) intervals on severaV 

 of the younger internodes of plants of Phaseolus growing in soil 

 and determine the region of elongation of the stem. Determine 

 also the total growth in successive internodes of a mature plant 

 and develop a graph of the results. 



Remove carefully the leaves from a node or two of half -grown 

 oats or rye, mark off parallel lines on the internodes both near 

 the basal and the upper parts, and describe the elongation phe- 

 nomena, preserving the plants, if possible, under moist con- 



FIG. 90. Force of growth in the ostrich fern ; leaves breaking through 

 concrete pavement. [After Stone.] 



ditions. Study and prepare a curve of growth for the scape of 

 dandelion, using plants growing either in the field or under green- 

 house conditions. 



Extension of leaves. Study the rate of development of broad 

 leaves such as those of grape, squash, or bean, measuring on 

 successive days or periods both length and breadth. 



Secure branches of one or more trees in winter condition, such 

 as lilac, beech, poplar, and apple. Determine the average 

 number of nodes produced by a season's growth and compare this 

 with the number of nodes or leaves found by the dissection of 

 half a dozen buds. 



Growth in tissues. Dissect out the growing point of Elodea 

 or Hippuris, mount in water under a cover glass, and examine. 



