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THE POPULAR SCIENCE MONTHLY 



mechanically restrained by the use of plaster-of-Paris casts, and from 

 2 to 6 atmospheres for the radial pressure of roots. The geotropically 

 sensitive nodes of the wheat stem gave a pressure equal to 15 atmos- 

 pheres when mechanically restricted. The maximum osmotic pressure 

 in these cases would be obtained by a solution of potassium nitrate 

 equal to about 5 per cent. 



Colonel W. S. Clark's experiment with the lifting power of a squash, 

 made in 1874 at Amherst, was one of the first attempts to learn the 

 growing power of plants. This experiment attracted quite a little 



Fig. 9. Method of demonstrating clasping power of tendrils. 



attention at the time. One highly respected minister of the gospel had 

 a drawing of the harnessed squash distributed among his congregation 

 in tract form to illustrate the great moral principle that " If God in 

 his providence has given such enormous power to growing vegetation 

 to overcome difficulties, how much more will he give to you power to 

 overcome the difficulties that may be in the way of your reaching the 

 true end of all living." 



This experiment was carried on in a greenhouse under the most 

 favorable conditions, and by arranging an iron harness provided with 

 a lever attachment the squash was found to raise 5,000 pounds. The 

 squash was horticulturally known as the Mammoth Yellow Chile 

 variety, and at the close of the experiment weighed 47-J pounds. It is 

 estimated that the squash developed over 80,000 feet, or about 15 

 miles of roots, an average of about 1,000 feet daily. From the data 

 given in this experiment we have been able to estimate roughly the 

 osmotic pressure of the cells, which might be supposed to be most active, 



