36 Elementary Plant Physiology. 



similar lot in distilled water for the same length of time. Place 

 all of the lots in a suitable germinator, and note results. 

 Compare the action of this substance with that of common salt. 

 Repeat the test with a i per cent, solution, but soaking 

 one lot for 30 minutes, another for an hour, another for two 

 hours, and another for three hours. What is the effect of 

 lengthened exposure to this substance? Does its deleterious 

 effect increase in a degree corresponding with the length of 

 time of exposure ? 



28. Epinasty and hyponasty. Observe the fronds of 

 some large fern such as Woodsia or Osmunda, and note that 

 the apices are curled upward into a compact roll. This position 

 is due to the fact that the lower (outer) side is growing faster 

 than the upper, constituting hyponasty. Later the upper side of 

 the frond begins to increase its rate of growth, and in conse- 

 sequence the frond is gradually unrolled, finally lying in one 

 general plane. Inequalities in the rate of growth thus cause 

 many organs to assume different positions at various stages of 

 their development. 



Follow the course of growth of leaves of some plant forming 

 rosettes, such as the thistle, mullein, or dandelion, at various 

 ages, and note the positions of the leaves resulting from epi- 

 nasty. Mark the surfaces into intervals, as in 8, and de- 

 termine the location of the growing regions. Extend these 

 observations to include leaves unfolding from buds of perennials. 



Follow the movements of the leaves of any onion (A Ilium) 

 during their development from a bulb. 



Make a series of sketches showing the successive positions of 

 the parts of the calyx, corolla, stamens, and pistils of any poly- 

 petalous flower during its opening and development. (See 

 " Carpotropism.") 



29. Correlations. Select a vigorously growing specimen 

 of some young tree, or any convenient perennial, and decapi- 

 tate it by removing the apical bud at the end of the main 



