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THE POPULAR SCIENCE MONTHLY 



to flow from the host to the tissues of the parasite carrying substances 

 in solution. The experimentation in this subject consisted, first of all, 

 in forming artificial parasitical relations between plants in order to ob- 



1909 1910 1911 1912 1913 



Fig. 4. Graphs Showing the Water Relations of a Large Cylindrical 

 Cactds when Separated from a Source of Supply for Extended Periods. The 

 lower line shows the weight decreasing from 38 kg. to 28.8 kg. in five years. The 

 upper line shows the rate of daily loss which fell from 10.6 g. to 3.5 g. during this 

 time. The rate of loss is not directly proportional to the succulence or amount of 

 water present. 



tain a number of couples which might be joined as host and dependent, 

 and also equally important to find others which might not enter into this 

 relation. 



The succulents with their accumulations of water offered suitable 

 material and, using these as artificial hosts a number of species were 

 caused to live on them parasitically for months or even years. Having 

 this material, analyses of the sap or watery solutions of the two plants 



